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A police investigator walks into a room. He sees two dead bodies on the floor, those of the unfortunate duo Alice and Bob, the players in many physics thought experiments. They had been locked in the room together. The investigator notices several things:

  • The door was sealed, and remained sealed since Alice and Bob were locked in one day before.
  • There is a broken window high up on the wall, with shattered pieces of glass all over the floor. The investigator finds that it is impossible to reach. The window was not broken when Alice and Bob were locked in. There are no other exits besides this window and the door.
  • There is a table by the window approximately four feet in height. Even an unlucky fall wouldn't have killed a person.
  • Security camera footage shows that nobody - living or dead - entered or exited the room. No inanimate objects entered or exited the room, either (obviously, things like light and air would have passed through the broken window). The footage is accurate.
  • There is a glass on the table, which has also been broken. It appears that it was a glass of water, because water was spilled all over the floor.
  • There is nothing else in the room - including no weapons.
  • Alice and Bob's bodies appear unharmed. There are no traces of poison.
  • Prior to being locked in the room, Alice and Bob had everything they needed to survive - food, water, oxygen, etc.
  • Alice and Bob died before the investigator opened the door.

The investigator relates all this information to his supervisor. The supervisor cannot solve the puzzle, yet the investigator, smiling, says that he knows the answer.

How did Alice and Bob die?

Note: This isn't a riddle of my own devising. A friend of mine got it from somewhere, and related it to me.

HDE 226868
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    were Bob and Alice cats? Because this sounds familiar ;) – LinkBerest Mar 04 '16 at 02:20
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    If Alice and Bob turn out to be cats or fish, I have a few questions about what department my tax dollars are funding. – FraserOfSmeg Mar 04 '16 at 04:52
  • Did they swallow water they were drinking down the wrong pipe, and choke to death? – MicroMachine Mar 04 '16 at 08:17
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    @JGreenwell As a follow-on, was the inspector's name Schrödinger? – Hugh Meyers Mar 04 '16 at 08:45
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    Never heard of Schrödingers fishes so why expeting fishes? but ok xD And uhm.... I'm confused about: "The investigator notices [...] The footage is accurate." How he can do this on the spot? And this makes me curious since you not at one time mentioned it: Is what the inspector actually notices given to be true? Or is he maybe noticing wrong, or even lying to the "audience"? It is actually not excluded by the current statements :) – Zaibis Mar 04 '16 at 11:32
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    @Zaibis It's an assumption I'm asking people to make. Someone suggested that the footage could be wrong; I had not intended that. – HDE 226868 Mar 04 '16 at 12:41
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    I'm not sure of the "how", but I'm pretty sure I know the "who". It was Mallory. Don't believe me? Ask Eve. She always seems to know what's going on between those two... – Parthian Shot Mar 04 '16 at 15:00
  • Just watch the security footage. – Trenin Mar 04 '16 at 15:11
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    They were mayflies, which have a lifespan of one day. The broken glass is inconsequential. – MackTuesday Mar 04 '16 at 17:39
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    My guess is they were summoned into yet another physics thought experiment which ended badly for them: https://xkcd.com/669/ – thanby Mar 04 '16 at 18:09
  • Should we assume they were alive when they entered the room? – kasperd Mar 04 '16 at 18:38
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    They actually left a detailed description of what was going on, but sadly in addition to physics, Alice and Bob were master cryptographers and no one could figure out what the message said... – corsiKa Mar 04 '16 at 19:23
  • @JGreenwell No comment, save that curiosity did not kill them. – HDE 226868 Mar 04 '16 at 22:59
  • @fabriced Feel free to make that an answer, although that seems like it could leave water in the lungs. – HDE 226868 Mar 04 '16 at 23:00
  • @kasperd That's an assumption I had made initially, but others have since answered otherwise, so no, you don't have to assume that they were alive. – HDE 226868 Mar 04 '16 at 23:01
  • @HughMeyers and if his name was such - were they really dead before he opened the door? ;) – LinkBerest Mar 04 '16 at 23:05
  • Alice and Bob have been in as many IT and CS thought experiments and diagrams as Physics. They get around. – Hack-R Mar 05 '16 at 02:39
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    If it's fish or cats or whatever then the statement "the players in many physics thought experiments" is false, unless you've clandestinely written up "many" unpublished physics thought experiments regarding Alice and Bob as non-people. – djechlin Mar 06 '16 at 20:39
  • "There is a table by the window approximately four feet in height. Even an unlucky fall wouldn't have killed a person." I think you underestimate the world's ability to damage biological entities. – jpmc26 Mar 06 '16 at 22:09
  • @djechlin I wrote the question well aware of that fact, and wrote that phrase as something of a red herring. Note that many of those thought experiments never state that Alice and Bob are humans. Fish experience time dilation just as humans do. – HDE 226868 Mar 06 '16 at 22:12
  • @jpmc26 Perhaps I do. But people/fish/etc. will continue to find creative ways to hurt themselves using tables of any size. I considered that issue, but couldn't find a good solution. – HDE 226868 Mar 06 '16 at 22:13
  • Given the answer, the table seems unnecessary. The glass could just as easily have been sitting on the floor. It would still be recognizable as not part of the window by the shape, and you could indicate it was opposite the window for extra good measure. – jpmc26 Mar 06 '16 at 22:16
  • @jpmc26 I suppose I could have; you're right. I was going to reply that it would seem odd to put a container of goldfish on the floor, but then again, this entire scenario is odd. – HDE 226868 Mar 06 '16 at 22:18
  • While I don't know the origin, I know this 'puzzle' as a story for a "ask as many Yes/No questions as you like"-game. In fact, I played this game over 20 years ago with my teacher! While such things are "fun", I don't think they are puzzles but rather an exercise in creative-story-telling.... – BmyGuest Mar 07 '16 at 10:31

16 Answers16

69

We are asking the wrong question:

* The security tapes show that nobody else entered the room, and we are told that the inspector is the one to have unsealed the door.
* We are told everything which was in the room, and there was no method of communication that could have been used by Alice or Bob to have summoned the police themselves.
* So the most important question is: since nobody found the bodies, and since Alice and Bob could not have summoned the police themselves, why was the investigator even there, unsealing the door?

The only rational answer to this critical conundrum ("why was the inspector there?") is that the inspector must have already known the bodies were there to be found.

And therefore..

The investigator must have killed Alice and Bob some number of days in the past, and then sealed their bodies into the room in order to conceal his crime, and then returned to "discover" their bodies the next day.

Critically, note that the puzzle never actually specifies that Alice and Bob were alive at the time of being sealed into the room. Since we've established that they died at some point before the inspector unsealed the door, and that nobody killed them while they were sealed inside the room, the only logical conclusion is that they had died at some point before even being sealed into the room in the first place.

As a result, the investigator gets away with his shocking crime, and gets to smile enigmatically as he informs his supervisor that he knows how it happened. And then invite him out to dinner, and maybe back to his place for afters. Maybe his supervisor would finally notice him now!

Trevor Powell
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    Sometimes I feel like lateral-thinking is the fanfic of puzzles. :) – Trevor Powell Mar 04 '16 at 06:56
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    We have definitely passed into the fanfic zone on this one. This is quite an old puzzle and I am sure many other experienced puzzlers on this site share my fond memories of struggling through this and similar puzzles in our childhoods. Consider these answers as a tribute to an old friend. – Hugh Meyers Mar 04 '16 at 13:50
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    The "inside job" conclusion is the best conclusion, and I applaud it wherever I find it. Was it an accident I was overcharged for that muffin, or was it... CONSPIRACY? – Parthian Shot Mar 04 '16 at 15:05
58

The investigator knew, as the supervisor did not that

The room was not heated!

and

There was a sudden, catastrophic cold snap the night before.
The extreme cold caused the metal window frame to contract, breaking the glass.
The water in a sealed glass container froze, breaking it.
When temperatures returned to normal in the morning, the ice melted.
Therefore, Alice and Bob died of hypothermia. I know this is the right answer because OP cleverly hid the word "ice" in Alice's name. The remaining letters are an anagram of BLABO, an oil tank cleaning system described here.
This is the last piece of the puzzle. Clearly, the reason the room wasn't heated was because the oil tank for the furnace was being cleaned with BLABO.
And the investigator smiled at this tragedy. That sick, sadistic so and so!

Hugh Meyers
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36

Alice and Bob...

...are actually fish! They were in a glass fishbowl on the table that had shattered, perhaps due to an unfortunate resonant frequency*. This frequency also broke the glass window. This explains the broken glass and water on the floor, and the two dead (but otherwise uninjured) fish :(

Edit*

For completeness sake I'm gonna say that a passing ambulance was blasting a siren at said resonant frequency.

AZGreenTea
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    But how could fish be those "players in many physics thought experiments"? I'd really like to see fish deal cards or write numbers on a board! And then logically... no, Thor seems much more likely a reason ;) – Paul Evans Mar 04 '16 at 02:18
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    @PaulEvans - I read that as a nod to the many thought experiments that involve an "Alice" and a "Bob", rather than part of the riddle itself. See https://en.wikipedia.org/wiki/Alice_and_Bob – BenM Mar 04 '16 at 03:22
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    D'oh! I knew I'd heard this one before. Twice. For some reason it comes off way different in writing. – Will Mar 04 '16 at 04:08
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    I as a taxpayer want to know why police investigators investigate dead fish to that level of thoroughness. – Joshua Mar 04 '16 at 05:02
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    @Joshua: Normally, you'd be right but in this case, the Chief Constable believed there was something fishy. – Magoo Mar 04 '16 at 05:26
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    @PaulEvans An 82-kg Alice and a 48-kg Bob are gliding across the ice at 7.4 m/s towards each other. Assuming momentum conservation, determine the speed and direction of the two fish immediately after the collision. – AZGreenTea Mar 04 '16 at 05:45
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    @Joshua What can I say, they were really carp at their job. – AZGreenTea Mar 04 '16 at 05:51
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    What's worse is that the supervisor couldn't solve the conundrum of the dead fish on the floor – mowwwalker Mar 04 '16 at 07:36
  • The physics experiments could relate to them crashing into the side of the bowl or jumping out of it. Or hail came through the window and broke the fishbowl. All of which could lead to broken glass and water on the floor. – Z. Dailey Mar 04 '16 at 07:57
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    It's a puzzle site, not a physics site, but I have a hard time with this answer. Square windows basically can't break from resonant frequencies. Additionally, it would be practically impossible to get enough sound energy inside the room to break the fish bowl from outside. Even a bomb going off on the roof would be hard pressed to break it without direct line of sight. – MichaelS Mar 04 '16 at 10:42
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    @MichaelS When I originally heard this puzzle, the room was near an airbase and the window and bowl were broken by a sonic boom. This certainly works for windows. I share your skepticism on the bowl. – Hugh Meyers Mar 04 '16 at 13:42
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    This is very close to the answer I had been looking for. I had originally intended for some sort of strong breeze to have been the culprit, but successfully figured out that the key was that Alice and Bob are (were) fish. – HDE 226868 Mar 05 '16 at 01:20
  • Perhaps Alice and Bob were experimenting with the same phenomenon that happened to the Incredible Mr Limpet , and morphed back to human form after the bowl shattered and they hit land again. This will explain why the police are investigating – Knight0fDragon Mar 07 '16 at 17:10
  • I came up with the fish answer first! – HankCa Mar 07 '16 at 21:21
  • @Joshua, The constable investigated for the halibut. – Mark Kasson Mar 10 '16 at 00:38
  • I don't think it makes sense for there to be an investigator assigned to the death of some fish. – levininja Nov 24 '16 at 05:48
18

They were killed by:

Lightning!!!!

Because:

They both had their hands on the glass of water (probably due some complicated competition of a mathematical nature) and at the exact moment water poured out of the glass and onto the floor in a continuous steam forming a perfect circuit to ground - a bolt from Thor (who may of been a bit jealous) crashed through the window! Ever so lightly zapping them into another dimension.

The investigator knows because:

He is Thor (working in his day job)

Paul Evans
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    Creative, although not what I'm going for. Would someone struck by lightning show evidence of being struck, though? – HDE 226868 Mar 04 '16 at 01:43
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    Hmmmm, got me there. Suppose even Thor couldn't have zapped them that lightly if he had to smash through a window to get them. – Paul Evans Mar 04 '16 at 01:47
  • Or Mjölnir just crushed the window? – Falco Mar 07 '16 at 13:01
  • @Falco Of course! The old double whammy... take out the window with Mjölnir and then zap Alice and Bob with just enough juice to finish them off but leaving no trace. And Thor can do this so quickly, between security camera frame snaps even. – Paul Evans Mar 07 '16 at 15:14
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    I wish this was asked by @Randal'Thor ... that would be ironic... – Omega Krypton Feb 08 '19 at 11:51
15

Alice and Bob

suffocated.

because

there was no oxygen in the room to begin with. "Prior to being locked in the room, Alice and Bob had everything they needed to survive - food, water, oxygen, etc." Presumably the air was vacuumed out after the room was sealed. The investigator opening the door caused air pressure to rapidly equalize, breaking the glass and the window.

Robert
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  • If it was a complete vacuum, the door would have been impossible for the investigator to open, given the atmospheric pressure on it from the outside – mowwwalker Mar 04 '16 at 08:06
  • Next to that, their bodies would have exploded during the vacuuming. – Stephan Bijzitter Mar 04 '16 at 08:23
  • The door could be opened if there's a small latch or something that allows a little air in. The bodies wouldn't explode, but I expect it would do something like rupture capillaries and extremely dry out the skin. Plus the water would have evaporated. – MichaelS Mar 04 '16 at 09:55
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    @mowwwalker If the door opens outwards, sure it's nigh impossible to open, but if it opens inward, all it basically needs is for someone to nudge the handle down and the air pressure will fling it open. – Robin James Kerrison Mar 04 '16 at 10:54
  • @Stephan hardly - the human body in a vacuum stretches to about double its current size, but even if you were ejected into space you would survive unharmed for around half a minute if you could make it into another airlock (and fit through it...) Your blood continues to flow and you stay fairly warm. – corsiKa Mar 04 '16 at 19:30
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    @RobinJamesKerrison You're right, and the doors to locked rooms always open inwards in order to keep the hinges on the inside of the room. – Probst Mar 04 '16 at 20:23
  • @corsiKa I find that hard to believe, do you have source for that? – Stephan Bijzitter Mar 05 '16 at 09:33
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    @StephanBijzitter Why is it hard to believe, and why would you expect it to explode? Too many movies for you, I think. In any event Wikipedia has a halfway decent article on the matter: https://en.wikipedia.org/wiki/Space_exposure – corsiKa Mar 05 '16 at 19:23
  • @corsiKa No need for the condescending touch. I just underestimated the strength/flexibility of the human body. – Stephan Bijzitter Mar 06 '16 at 09:47
14

Unbeknownst to anyone there was a large block of dry ice in the room. It sublimates so fast that it filled the room with CO2 suffocating Alice and Bob. One of them had a glass of water which slipped from their hands to the floor. The extra pressure caused the window to break open.

Dr Xorile
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    Wouldn't the glass of the broken window be outside, not inside? – Erics Mar 04 '16 at 03:04
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    Glass always falls both ways – Dr Xorile Mar 04 '16 at 03:20
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    @Dr Xorile No, it depends on where the pressure is added. – Scott Mar 04 '16 at 04:59
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    So you're saying that I was wasting my time wearing goggles when working with evacuated glass tubes? Because the glass would only have gone inwards? :-) Brittle materials tend to have material going all directions when they fail. I agree that the majority of the glass would probably have been outside, but I wouldn't be shocked to find some glass inside. – Dr Xorile Mar 04 '16 at 16:52
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    A variant on this: Someone threw the dry ice in through the window, that's why it's broken. – Loren Pechtel Mar 04 '16 at 19:02
  • Wouldn't suffocation by CO_2 show evidence of poisoning, which is ruled out by the problem? (Actually the problem appears to have been edited to rule out some undesireable answers, so I don't know whether it was there when you posted this.) – LSpice Mar 06 '16 at 18:26
  • CO2 is not poisonous – Dr Xorile Mar 06 '16 at 18:46
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    And if two fish suffocation from a lack of oxygen is considered the right answer, two people suffocation should be ok! – Falco Mar 07 '16 at 13:00
9

The room was pumped with carbon monoxide prior to Alice and Bob being locked in. They don't notice at first, but start to feel light headed and decide to throw the glass of water at the window to get some air. It's unfortunately too little too late and there isn't enough time for the carbon monoxide to fully disperse before Alice and Bob are killed by carbon monoxide poisoning.

mowwwalker
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8

Alice and Bob both suffered from a chronic condition that required them to take pills twice a day. They had taken with them into the room a glass of water for that purpose. At the beginning of their stay inside the locked room, Alice dozed off and Bob decided to scare her and wake her up. When Alice woke up, she was so startled that she screamed at just the right pitch to shatter both the window and the glass of water. Having lost the water they needed for their pills, they both died within hours.

Pedro
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7

I'd think this one would be obvious.

Outside the window was another small enclosed space, containing a fan. The fan was blowing SO HARD that it broke the window and knocked the glass of water over. Alice and Bob were unfortunate victims of fan death. When in doubt... Fan death.

Alternative answer to the question "How did Alice and Bob die?":

Mysteriously.

Parthian Shot
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Alice and Bob were trying to Science the Shit out of some hydrazine to create water for growing potatoes.

Unfortunately they forgot about the Oxygen they were breathing out and blew themselves up.

Take that Neil Armstrong!

Aron
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4

Alice and Bob were performing physics experiments. There is a chance of fire in the room and must have produced lots of smoke and they would have started suffocating can't use oxygen because it will ignite fire more tried to break the window using the glass but it was too late for them, enough carbon was inside their lungs to suffocate them and they died.

Gamow
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vikash
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4

The "room" is a submarine.

When the exterior pressure got too high during a descent, the high window shattered inward and the submarine flooded, causing both Alice and Bob to drown (and incidentally breaking an otherwise unrelated Crimson Flounder™-brand drinking glass that happened to be present). The flooding also accounts for the water on the floor. (In fact, there was rather a lot of water on the floor. And almost everywhere else.)

The room being a submarine also explains why the room would contain a supply of food and water, why there are no weapons to hand, and why the room would even be sealed in the first place.

Presumably the inspector accidentally discovered the remains of the room (and thereby the bodies of Alice and Bob) while engaging in some scuba training, in an effort to gain some impressive new skills which would cause his dreamy (but frustratingly tsundere) supervisor to finally notice him.

Trevor Powell
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2

Alice and Bob are / were fish and were in the glass of water. A bird saw them or for other reasons flew into the window and broke it. A piece of glass dropped and knocked the glass off the table and on to the floor thus dislodging the fish from the water and hence asphyxiating them.

HankCa
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0

Perhaps there was a downpour of rain, and the two drowned?

Tboz
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-1

There was a sound so horrible it killed Bob, Alice, the window, and glass of water.

bb216b3acfd8f72cbc8f899d4d6963
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-3

Alice and Bob's last work assignment was participating at a physics experiment at CERN, and unbeknownst to them,

a tiny black hole had gotten stuck in Bob's throat.

It slowly grew, until Bob sneezed. The extra velocity and the glass of water it hit caused it to grow rapidly, sucking out all the air in the room. Unfortunately Alice and Bob suffocated before the window burst in.

jpa
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