The rules, in four lines
- There are five suspects and a grid of five by five cells, divided into rooms.
- Each suspect occupies one cell, and there is exactly one per row and one per column. Never two in the same row or the same column.
- The victim sits in a fixed cell, marked 💀. Nobody can occupy it.
- The room holding the body ends up with exactly one person in it: that is the murderer. It is not hidden information, it is a rule you can deduce with.
Every clue is true. There are no trick clues, no lying witnesses and no hidden twists: if a clue says the countess was in the conservatory, she was in the conservatory.
How to crack a case
1. Start with whatever pins a cell
Clues are not worth the same. «Was in row 3» or «in column 2» nails a whole coordinate; «was in the lounge» only narrows things to a group of cells. Place what is certain first and leave the vague for later: every person placed removes a row and a column for everyone else, and that is what starts the avalanche.
2. Treat the row-and-column rule as another clue
This is the commonest mistake: reading the clues and forgetting the rule. With three people placed there are only two free rows and two free columns left, so the other two have four cells to share between them — and the rooms often rule out two of those at a stroke.
3. Negative clues are worth more than they look
«Was not in the kitchen» seems slight, but if the kitchen is four cells, you have just removed four possibilities for that person. And «never set foot in the room with the body» is better still: it is telling you outright that this person is not the murderer, which shortens the suspect list before you have placed anybody.
4. Leave the accusation for last
The temptation is to guess the culprit from the first clue. It does not work, and it distracts you: the culprit is a consequence of the arrangement, not an independent fact. Place all five first; the name falls out on its own.
5. If you stall, count rooms
When there is a clue like «there were exactly two people in the dining room», use it as a global constraint and not as a detail. Combined with the row-and-column rule it usually closes the case in one go, because it caps how many cells in that area can be occupied.
Where this comes from
The genre was popularised by murdoku, a format crossing the logical placement of sudoku with a crime scene, which reached a wide audience through the book by Manuel Garand. Before that there were already the old logic riddles — the «five houses, five colours, five occupations» kind — which use the same reasoning without the map.
We call our cases Criminoku and we generate them ourselves: we pick a setting, place the suspects, work out every clue that would be true, and then strip clues away for as long as the solution stays unique. That is why each case carries the minimum clues needed, and why we can promise there is no guessing: it is verified case by case.