# Detectives vs Nelson: The Chessboard Serial Killer

This is about Nelson, a serial killer who, after each murder, leaves a chess diagram in the scene of the crime. These chessboards give the detectives the opportunity to decipher where, how and when Nelson will perform again. (Note: you should know how chess is played and how chessboard squares are enumerated).

Detectives Brandon and Makeda are the two agents in charge of these murders. Brandon, who is the superior of Makeda, won’t forget his black hat under any circumstance. There are also 2 things worth noting:

1. Both detectives are left-handed.
2. When investigating a corpse, they like keeping as close as possible to it.

Scene 1 (26/Jan/2016)

It is known this was the second victim of Nelson; the remains of the first victim were never found.

The lifeless body of a 19 year-old teenager was found hanging upside-down a tree. Right under the body, detectives found the first diagram and a very particular weapon next to it. Under the diagram there was a note:

You first, Makeda. Do it the best you can. And remember: I'm always one step ahead of you both.

Scene 2 (27/Feb/2016)

At the scene, the detectives found an old man’s body, with two shots to the head. Next to the body, there were three bullets; it seems that one of them was never used. The serial killer left this chessboard, with some g/unpowder spread all over the pieces. There was a note:

I love how weak my victims are, detectives. That's the beauty behind murdering people.

Scene 3 (10/Apr/2016)

Detectives were feeling really agitated. Three murders in less than 3 months. They needed to stop this massacre, so this last chessboard was crucial to find a pattern and predict the next place for a possible crime.

A beautiful, mid-aged woman had her hands and feet tied down, three shots to the chest. She was lying on the grass, and there was no evidence she had been abused. Again, the typical chessboard next to her, with a note:

You move again, detectives. And know, by the way, I just broke down your car. Mine is wrecked as well, but that won't stop me.

Know, by the way, that while you are reading this note, I am killing my 5th victim! There I won't leave any chessboards whatsoever. Will you stop me before I kill my 6th victim?

Scared of what they just read, they knew there was going to be a 5th victim. Having these diagrams and notes, detectives need to find out:

1. Where (square) will the detectives find the 5th poor soul?
2. Where (square) will Nelson try to kill his 6th victim?
3. When (day and month) does Nelson intend to kill the 6th victim?
4. Can you say anything about how (weapon/method) Nelson intends to murder his 5th victim?
5. Nelson said he wouldn't leave any chessboards in Scene 4, but if he did, what would that chessboard be?

(Note: the dates indicated for each scene, are the dates for which detectives Brandon and Makeda find a dead body on the scene of the crime. This concides with the date when the next victim is being murdered.)

Hint 1

First, try to determine what role each piece play (i.e. Brandon, Makeda, Nelson and the Victim). You will note there are two extra pieces. Read through all notes carefully, and in particular, the 3rd note will give you a clue of what those 2 excess pieces are.

Hint 2

The number of shots doesn't mean anything - it just adds value to the story. The date of crimes doesn't mean anything either, but they do follow a pattern you need to guess.

Hint 3

Detectives suspect that the weapons used to commit the crimes will help them identify which chess piece is playing the role of the serial killer. As some of you have noticed, I wrote g/unpowder instead of gunpowder, and this is not casual. By the way, detectives need to know the name of the weapon used in Scene 1. Can you help them?

• "won't forget his black hat under any circumstance": xkcd ref? ;) And by the way, great question. – gcampbell Jun 4 '16 at 19:09
• Thanks gcampbell! What is xkcd ref? No, it's just a black hat, no tricky words here! :P – Jose Lopez Garcia Jun 4 '16 at 19:12
• xkcd: one of the characters is called Black Hat. – gcampbell Jun 4 '16 at 21:30
• Oh! No, gcampbell. I'm talking about a real black hat, which in turn has something to do with the pieces on the board. – Jose Lopez Garcia Jun 4 '16 at 21:34
• Very nice puzzle idea and story framing. It's great to see some "new" creativity on this site and not just endless variants or "5-min-riddles". +1 – BmyGuest Jun 5 '16 at 9:26

All questions asked I have answered, with the mate-in-n idea from @RosieF. Whether my answers are correct, I have yet to see.

Pieces:

White king: Nelson's car
White Knight: Nelson
White pawn: victim
Black king: detectives' car
Black queen: Makeda
Black bishop: Brandon

Weapons:

The Flail was found when the knight/Nelson was in the 'F' file, and The Gunpowder was found when the he was in the 'G' file. It seems likly that Nelson's only other weapons are an Axe, a (uh, Boomerang?) , Club, ... you get the idea.

1.

The knight is always where the victim will be, so the 5th victim is at g4

2.

The 6th murder will be at g5 (see Q#5)

3.

A comment from Jose says the pattern only has to do with the knight's position and the pawn's rank. In the first board the knight's rank, then the pawn's rank make 26, on the 26th day of the year. On the second board, they make 32, and the (26 + 32) 58th day of the year is Feb 27. Adding 43 from the last board on a leap year results in Apr 10. If the (Q#5) chessboard is correct, it will happen in 54 days, or June 3

4.

The fifth will have been done with a gun, the sixth with another gun.

5.

Reasoning: From the third chessboard: Both kings will be in the same positions as before, because they are broken. Both other black pieces do not move, because they can examine the body from where they are. The pawn will be where the knight was (see Q#1). Looking for mate in five position for Knight... Found! [G5].
Moves: 1.) ...Qh1+ 2.) Kg6 Qd5 3.) Kg7 Qxg5+ 4.) Kh8 Be5+ 5.) Kh7 Qg7#

• So far so good. For number 2, see @RosieF's answer about the mate-in-$n$ problem. – Jose Lopez Garcia Jun 13 '16 at 16:44
• If you're able to answer from 1 to 3, I'll give you the +100 rep points, since they expire in 2 hours. – Jose Lopez Garcia Jun 13 '16 at 16:45
• Almost there @ash4fun. But Nelson cannot be in the 4th rank for the last murder. Note that the position of the knight has actually something to do with the number of the victim he is killing. Good point about the kings being broken (they are the cars, as you said). You are ALMOST there, you just need to modify the diagram and answers 2 to 4. For the date, have into account that both the rank of the previous victim (pawn) and the actual position of the Knight (Nelson) are the only pieces to be considered. You just ALMOST got it right, give it another try! I have 4 hours to award the bounty. – Jose Lopez Garcia Jun 14 '16 at 14:41
• Are you sure your position is mate in 5? – Jose Lopez Garcia Jun 14 '16 at 19:51
• Hint: observe that in the Scene 1, knight is in the 2nd rank and pawn is in the 6th rank, so.... – Jose Lopez Garcia Jun 14 '16 at 19:52

Black queen:

Makeda the detective. @RosieF found that googling Makeda returned the Queen of Sheba. She is left-handed: "greeting the queen with his left hand." (http://emc.eserver.org/1-3/jones.html)

Black bishop:

Brandon the detective. "won't forget his black hat" -- bishops wear hats, and this bishop is on Black's side. He's the queen's superior because he's always a rank above her. Also, the bishop is always on a black square (not sure if this is intended or not.)

White knight:

Nelson the murderer. In scenes 2 and 3, the number of shots the victim is hit with is the number of moves necessary to get from the knight to the pawn. Apparently the number of shots doesn't matter. But @RosieF has pointed out that one of George Washington's horses was called Nelson. (I don't know why I was thinking of Nelson's Column...)
(@Jasen:) On each board the position of the knight indicates where the victim will be found on the next.
(@Bulldogg6404:) The weapons used tell us which file the serial killer's piece is. flail begins with f (the f file) and gunpowder starts with g (the g file, also works with the wordplay "g/unpowder").

White pawn:

last (dead) victim. "I love how weak my victims are" -- pawns are the weakest piece. 2nd thing worth noting: "the detectives like keeping as close as possible to the corpse". So this must also mean that black queen/bishop are the detectives.

Black king and white king:

The kings are the extra pieces: 3rd note says "I just broke down your car. Mine is wrecked as well, but that won't stop me". In Slavic languages, "car" means "tsar"/"czar", the ruler/emperor. So the kings are the cars, and they're not working, but it apparently doesn't matter. Also, hint 1 "in particular, the 3rd note will give you a clue of what those 2 excess pieces are" implies that it is the kings.

The dates follow a pattern. Still not sure what the pattern is, thinking about it.

So:

1. Square G4? This would follow the pattern of the knight marking the position of the pawn in the next scene.
2. Maybe G5? This would just follow the pattern of the knight moving one square up each time. (Or is it something to do with the white king, in which case it would be H5? Or is it related to the dates?)
3. ?
4. ?
5. ?

Feel free to edit and add stuff.

• You are on the right track right now. Don't forget that, as you discover new things, you'll need to explain how you reached your solutions (giving only the solutions is not valid for an accepted answer) – Jose Lopez Garcia Jun 4 '16 at 22:24
• I am confident that you are correct about the identities of the victim and detectives. That leaves which piece is the murderer and which two are excess. I believe the killer is the white King because his position in the third chessboard creates a pin on their car, the white Knight (it cannot move, being broken down, but not wrecked, as in being captured and taken off the board). – Bulldogg6404 Jun 5 '16 at 1:02
• Another note, the weapons used tell us which file the serial killer's piece is. flail begins with f (the f file) and gunpowder starts with g (the g file, also works with the wordplay "g/unpowder"). The only piece that stands on those ranks in all three respective scenes is the knight - our serial killer. – Bulldogg6404 Jun 6 '16 at 2:48
• Come on guys, cheer up! This solution contains sufficient information to solve the first 2 questions! – Jose Lopez Garcia Jun 8 '16 at 21:29
• Why g4? Why g5? Where are kings placed in the final chessboard? – Jose Lopez Garcia Jun 9 '16 at 11:44

Fascinating! So far, I've noticed that, in scene 1,

Black to move can #2 by 1... Qf1 2 Kh2 Bc7#

and that in scene 2,

Black to move can #3 by 1... Qxf2 2 Ne2 Kg8/Kh7 3 N~ Qg1# I'm not sure that that's relevant, though: a long-range check goes with a close-combat weapon and a close-range check goes with gunpowder??

and that in scene 3

Black to move can #4 with 1... Qxg3.

Note that

these are the 2nd, 3rd and 4th murders. That is, the position left at the scene of the $n$th murder is that of a mate-in-$n$ problem, with Black to move and mate. And with the same material. Perhaps the bQ is Nelson and the bB his sidekick? And the bK the Mr Big who stays away from the action but throws in a waiting-move when needed, as in scene 2's 2nd move by Black? Or am I overthinking this?
Edited apropos Jose's comment of 20:14Z: Googling Makeda shows that she was the Queen of Sheba (I knew she was called Balqis; hadn't heard of the name Makeda before). So she's the bQ, then? And Brandon the bishop? And Nelson the wK, then? In scene 1, the wK was mated on h2; in scene 2, h1; in scene 3, either e6 or h8. I can't fit that info to the clues, though.

Apropos gcampbell's work

and Jose's later clues about how Nelson likes how weak his victims are, and how B & M like to keep close to the corpse -- yes, the victim being the wP now makes sense, but that means that in scenes 2 M destroyed the victim, and in scene 3 M destroyed the victim and Nelson.

Another thing that fits in with gcampbell's work is that

One of George Washington's horses was named Nelson.

As to the weapons,

the first one is a flail. So the first letter of the weapon's name labels the file on which Nelson/wN stands, in the diagram.

• Good observations! – Jose Lopez Garcia Jun 4 '16 at 19:56
• It took me quite a while to create this puzzle, hope you guys enjoy it – Jose Lopez Garcia Jun 4 '16 at 19:57
• You are overthinking a bit. The puzzle itself is a bit complicated, so don't worry to get it wrong at first! Each piece plays a role, but I'm not sure you got each role right. Start first trying to determine which piece corresponds to which person. Hint: Mr. Nelson has no sidekick! – Jose Lopez Garcia Jun 4 '16 at 20:14
• Good job googling that name, that gave you who is the bQ. Since both detectives are in the same team, you should have a clue of who is the other black piece (pay attention to his name). With time, things will start to make sense (anyway I will be adding Hints from time to time, to help people in solving it!) – Jose Lopez Garcia Jun 4 '16 at 20:32
• @JoseLopez Don't add hints too quickly out of impatience. Good puzzles need time and you don't want to spoil your own fun. IMHO, it's better to have a good puzzle "linger" for a month than to spoil it too quickly by too many hints. Only when you think your puzzle is "dead" you should "revive" it with hints and/or bounties (if nobody else does it already.) – BmyGuest Jun 5 '16 at 9:32

(Edited to take account of a clue whose significance I hadn't previously realised:)

If Nelson did leave a chessboard at the scene of the 5th murder, it might play out like this:

The body of another teenage girl was found high up a tree, close to the scene of the second murder. She had been hacked to death. By the tree were an axe and a chessboard with this position

Reasoning: The same material as in the previous diagrams: white king, knight, pawn; black king, queen, bishop. This is pertinent because the chessmen other than the kings represent the characters in the drama, and the set of characters is the same as before. As in the previous diagrams, Black's queen and bishop are on the same file, with the bishop one rank higher than the queen -- perhaps because the bishop represents the superior officer. These black pieces are close to the pawn because "When investigating a corpse, they like keeping as close as possible to it", and the pawn represents the corpse. The previous diagrams solved as "Black to play and mate in $n$" problems with $n=2, 3, 4$ respectively; thus $5$ here.
The clue "Both detectives are left-handed" has just struck me -- now I guess that bishop and queen should be to the left of the pawn.
The problem solves as 1... Qg2 2 Nb4+ Bxb4 3 Kh5 Be7 4 Kh6 Qg8 5 Kh5 Qg5#

• Hey Rosie, thanks for adding your reasoning as @BmyGuest suggested. I upvoted because of your courage in being the first to attach a chessboard. The reasoning is very plausible, and you managed to interpret a lot of the hints the puzzle gives (maybe not all). However, the final position is not what you suggested. Also, the weapon is not right (good attempt though). Finally, you need to answer all of the 5 questions the puzzle asks at the bottom - giving your reasoning for each one! You are on the right track. – Jose Lopez Garcia Jun 5 '16 at 11:49

Thanks to another observation by gcampbell, that

in each scene the pawn is where the knight was in the previous scene. All other reasoning is as before.

If Nelson did leave a chessboard at the scene of the 5th murder, it might play out like this:

Another body was discovered, a little way above where the previous victim was found. Again there were traces of gunpowder. By the tree was a chessboard with this position

The problem solves as follows:

1... Qxg4 2. Kf6 Kd6 3. N~ Be5+ 4. Kf7 Qg7+ 5. Ke8 Qe8#/Qg8#. If 3. Kf7 then 3... Be5 or Bh6 also leads to mate in 5.
Unfortunately, if there'll be another murder where Nelson is now, Brandon and Makeda won't ever find the body if they continue to work left-handed.

• Although some of your pieces in the diagram you suggested are OK, it's still incorrect. This is because there is information you are missing. Why did you place kings that way? – Jose Lopez Garcia Jun 6 '16 at 10:42