How to solve Nosy: a village whodunnit, step by step

For the controls, scoring and strikes, see how to play Nosy. Here we concentrate on the thinking.

Three things that are always true

• Every clue is true, and so is the witness statement.
• There is exactly one complete arrangement of suspects, places and items (and times on Sunday). Our generator checks this with an exact solver.
• Every clue is needed. The generator removes any clue the case can do without, and checks that taking away any one clue leaves more than one possible arrangement. So if you reach the end with a clue you never used, something has gone wrong; and if you are stuck, the unused clues are where the answer is.

Cases grow through the week. Monday to Wednesday is a Village case with three suspects, Thursday to Saturday a Noticeboard case with four, and Sunday a Sunday special with five suspects and a time slot for each. Every case includes at least one either/or clue and at least one trail or time clue, so expect both.

What each kind of clue tells you

Is and is not

"Edwin Thimble is the person at the willow walk" is a tick, and the tick crosses out the rest of Edwin's places and everyone else's claim to the willow walk. "Is not" is a single cross. The interesting ones join two descriptions with no name, such as "The person at the duck pond is the person carrying the string bag". The notebook has a grid for places and a grid for items, but nothing that joins a place to an item, so keep these links on a note beside you. They are the clues players most often forget.

Linked pairs carry crosses across

Once you know the duck pond and the string bag belong to the same person, anything you learn about one applies to the other. If someone cannot carry the string bag, they cannot be at the duck pond, and the other way round. Every time you add a cross, check your list of linked pairs and copy it across.

Either/or

Either/or clues always offer two options from the same list, such as two items. Since a person has only one item, "one only" is automatic. What the clue really gives you is a set of crosses: the person described carries neither of the other items, and nobody carrying those other items can match that description. The best use of all comes when two either/or clues describe the same person and share an option. If the person at the cider press carries the envelope or the apron, and also the apron or the basket, the only item that satisfies both is the apron.

Trail and time clues

Places are listed in village trail order, so the first place is the start of the trail and the last is the end. "A was earlier on the village trail than B" means A is not at the last place and B is not at the first. Chains tighten this: if A is earlier than B and B is earlier than C, then A cannot be in the last two places and C cannot be in the first two. "B was one stop after A" is stronger: A is not last, B is not first, and as soon as one of them is placed, so is the other. If B cannot be at a place, A cannot be at the place just before it. On Sundays the same reasoning works on the time slots, which run every half hour from 10:00 to 12:00.

Worked example: Nosy No. 6

Nosy No. 6, "The wandering welcome sign", was a Noticeboard case on Friday 30 October. The suspects were Kitty Rookery, Edwin Thimble, Greta Wrenfold and Jemima Quill. The places, in trail order, were the duck pond, the cider press, the willow walk and the village hall. The items were a white envelope, a string bag, a canvas apron and a blue basket. The clues:

1. The person at the cider press is either the person carrying the white envelope or the person carrying the canvas apron (one only).
2. Kitty Rookery is not the person carrying the string bag.
3. The person at the cider press is either the person carrying the canvas apron or the person carrying the blue basket (one only).
4. The person at the duck pond is the person carrying the string bag.
5. Edwin Thimble is not the person carrying the blue basket.
6. Kitty Rookery was earlier on the village trail than Jemima Quill.
7. Edwin Thimble is the person at the willow walk.

The witness statement: a reliable witness saw the person at the village hall carry it away. Here is one clean route through it.

1. Clue 7 is a straight tick: Edwin is at the willow walk. Cross his other places, and cross the willow walk for everyone else.
2. Clues 2 and 4 together: the duck pond goes with the string bag, and Kitty does not carry the string bag, so Kitty is not at the duck pond.
3. Clue 6: Kitty is earlier than Jemima, so Kitty is not at the village hall (the last stop) and Jemima is not at the duck pond (the first). Kitty has now lost the duck pond, the willow walk and the village hall, so she is at the cider press.
4. Jemima must be later than the cider press, and the willow walk is Edwin's, so Jemima is at the village hall. That leaves the duck pond for Greta.
5. Clues 1 and 3 both describe the person at the cider press, now known to be Kitty. The only item in both lists is the canvas apron, so Kitty carries the apron.
6. Clue 4 again: Greta is at the duck pond, so she carries the string bag.
7. Edwin and Jemima share the white envelope and the blue basket. Clue 5 says Edwin does not carry the basket, so Edwin has the envelope and Jemima the basket.
8. Now the witness: the person at the village hall is Jemima Quill. The accusation is Jemima Quill, at the village hall, carrying the blue basket.

Notice that all seven clues were used, and that the witness statement only mattered at the very end. The complete arrangement and the light-hearted explanation are on the Nosy No. 6 answer page.

How our solver thinks, and what a hint means

Before a case is published, a deduction pass has to solve it without guessing. It works one clue at a time: for each clue, it throws out every way of handing out places (or items, or times) that could not possibly make that clue true alongside what is still possible elsewhere, then moves to the next clue, and repeats until nothing changes. That is why a hint reads like "Clue 6, together with the other clues and one of each per person, forces this square". In the case above, the pass got Jemima off the cider press straight from clue 6, because Kitty could no longer be at the first place, so the earliest Kitty could be was the cider press, and Jemima had to be later still. If a hint points at a clue you think you have used up, read it again with your current notebook in mind.

Before you accuse

A wrong accusation costs a strike and 100 points, and the game never says which part was wrong. Three strikes close the case. So do not accuse from a hunch: finish the notebook, check that every clue holds, and only then read the witness statement. It names a place or an item, never a person, so the last step is always to find who matches it.

Quick checklist

• Tick every direct "is" clue about a named person first.
• Write down every place-item link, and copy each new cross across it.
• Turn either/or clues into crosses, and look for two that share an option.
• Use trail and time clues for the first and last positions, and chain them.
• When stuck, find the clue you have used least. Every clue is needed.
• Fill the whole notebook before you read the witness statement and accuse.

Open today's Nosy case to try it, or replay any finished case from the Nosy answers archive. If you enjoy this kind of reasoning, our Sown techniques guide and why our puzzles never need a guess are good next reads.