Murdoku and murder-mystery logic puzzles

Updated 2026-10-30

Murdoku is a murder-mystery logic puzzle: you place a victim and a group of suspects on a floor plan so that no two people share a row or column, then follow the clues to find who was alone in a room with the victim. It mixes Sudoku-style placement with whodunit deduction.

What is Murdoku?

A Murdoku puzzle shows a building seen from above, drawn on a square grid. Walls split the grid into rooms such as a kitchen, a library or a garden. Inside the rooms are objects: tables, chairs, beds, plants, carpets and so on. Some cells hold objects people can stand or sit on, and some hold objects that block a cell entirely.

Next to the plan you get a cast: a victim and several suspects, each with one or more clues. A clue might say that a suspect was sitting on a chair, was standing next to a window, was in the same room as someone else, or was not in the kitchen. Your job is to put every person in exactly one cell of the grid.

The basic rules

The exact rules vary by book and edition, so always read the instructions that come with your puzzle. The common core looks like this:

1. One person per row and per column. Like digits in a Sudoku line, no two people may stand in the same row or the same column. On a 6×6 plan with six people, every row and every column holds exactly one person.
2. Clues fix where each person can be. Each suspect’s clues narrow down their possible cells, for example to one room or to a certain type of object.
3. Blocked cells stay empty. Some objects, like a shelf or a table, typically can’t hold a person. Others, like a chair or a rug, can.
4. Find the murderer. Once everyone is placed, the murderer is the suspect who is alone in a room with the victim.

Some editions add extra rules, such as people occupying certain objects, or special conditions for particular puzzles. The row and column rule and the “alone with the victim” rule are the heart of the format.

How to solve a Murdoku puzzle

Start with the most specific clue

Look for the person whose clues allow the fewest cells. “Was sitting on the only armchair” places someone immediately. Once a person is placed, cross out their entire row and column for everyone else.

Use rows and columns like Sudoku

After a few placements, check each row and column. If only one cell in a column is still allowed for anyone, then someone must stand there, and often only one person’s clues fit that cell. This “where can the last person go” question is the same reasoning you use in Sudoku and in placement puzzles.

Combine room clues

Clues like “was in the same room as the cook” or “was alone” link two people. Combine them with the row and column rule: two people in the same room still can’t share a line, so a narrow room might only have one valid pair of cells.

Don’t guess the murderer early

It’s tempting to name a suspect after a few clues. Resist it. The murderer only follows from the complete layout, and a careful fill of the grid is what makes the reveal satisfying.

Murdoku vs. Murdle-style deduction grids

Another popular kind of murder-mystery puzzle uses a classic logic grid. You get a short list of suspects, weapons and locations, plus a few clues and statements, and you mark a grid with X and ✓ until you know who did it, with what, and where. These whodunit grids are pure matching puzzles: there is no floor plan, and the challenge is linking categories together.

Murdoku is more spatial. The categories (who is where) are tied to an actual map, and the key constraint is geometric: one person per row and column. So while both formats end with naming a culprit, they exercise different skills. Whodunit grids train category matching and transitive reasoning; Murdoku trains spatial placement.

The placement idea behind Murdoku

The “one per row, one per column” rule isn’t new. It is the same core rule as the Queens puzzle, where you place one queen in every row, column and coloured region with no two queens touching. It is also close to Star Battle, where you place a fixed number of stars in every row, column and region, again with no two stars touching, even diagonally.

In Murdoku, rooms play a role a bit like the regions in Star Battle and Queens, except that a room may hold several people or none. The story and clues are what tell you who goes where.

Like the placement part? Try Star Battle

If the most fun part of Murdoku for you is filling the grid, crossing out rows and columns and spotting the one cell that has to be used, Star Battle gives you that feeling in its purest form. There is no story, just a grid of regions and a simple rule set, and puzzles range from easy one-star grids to tricky two-star ones. You can play Star Battle online for free, right in your browser. For more ideas, see our list of puzzles like Sudoku.