How to play

Murder OX is a logic grid puzzle wearing a detective's coat. You are never asked to guess and you never need outside knowledge. Everything you need is written in the clues.

The board

Every case has a set of suspects, a set of weapons and a set of rooms. Exactly one suspect goes with exactly one weapon and exactly one room — no sharing. The grid is where you keep track of what you know. Each square is a question: does this suspect go with this weapon?

The two marks

Tap a square once for ✕ — this pair is impossible. Tap it again for ✓ — this pair is certain. Tap a third time to clear it. Most of solving is putting ✕ everywhere; the ✓ marks tend to appear on their own.

Rule one: one per row and column

Because each suspect has exactly one weapon, once you write ✓ in a square, every other square in that row and that column must be ✕. And the reverse: if a row has ✕ in all but one square, the remaining square is ✓. This single rule solves most of an easy case.

Rule two: chaining

If the scarf was in the rose garden, and Dr. Sable was not in the rose garden, then Dr. Sable did not carry the scarf — even though no clue says so. Facts travel through the grid. This is where the harder cases live.

Naming the killer

Every case opens with one fact given away: where the body was found, or which weapon killed. Solve the grid and whoever matches that fact is your killer. Press the accusation button, pick the suspect, the weapon and the room, and the case closes.

The lying witness

In some cases each suspect makes a statement about themselves. The innocent tell the truth. The killer lies. Try assuming each one is the liar in turn — only one assumption will survive contact with the rest of the clues.

Never guess

Every case published here was checked by a solver before it went out. Any case that could be finished by guessing was thrown away. If two answers seem possible, you have missed a clue — not found a flaw.