Twenty Minutes, One Killer

Most elimination mysteries are one case that takes a month. This is 21 cases that take an evening each.

ONE SITTING. START TO FINISHED.

A register of 40 guests. Around a dozen clues. A killer who can only be one person. You sit down after dinner, you work it, you know the name before you go to bed.

That is a different product from a 48,000-name book, and it is deliberate. A single enormous case is impressive on the cover and exhausting on the sofa - and if you put it down for a week you have to start again, because you cannot remember which of your pencil marks meant what.

LARGE PRINT, AND THAT IS NOT A DETAIL

The most common complaint about these books is eyesight. Forty guests to a case instead of forty thousand means every register line is set in large print with room around it, and you can read it in the light you actually have in the room.

EVERY SUSPECT IS A PERSON

Not a name on a list. Each line of the register tells you:

- who they are - a churchwarden, a creditor, a bee-keeper, a former employee

- what time they arrived

- which room they were seen in

- what they were carrying

- what coat they were wearing

- whether they had been in the house before, and whether they came alone

Which is what lets a clue be about a person rather than about spelling. Nothing in here asks you to cross off every name beginning with S.

THE ELIMINATION COUNT IS PRINTED BESIDE EVERY CLUE

So you always know whether you have crossed off the right number. If a clue says it removes five and you crossed off four, you find out immediately, not at the end of the evening.

None of the counts is zero. A clue that eliminated nobody was thrown out by the program that built these.

ONE CULPRIT PER CASE, PROVED

Each case was built by choosing the killer first, generating every true statement about them, then adding clues until exactly one guest survived - and then re-testing all 40 suspects against every clue from scratch to confirm that exactly one does.

21 cases. 21 proofs. No case in this book was checked by somebody reading it over and thinking it seemed to work.

WHAT IS IN THE BACK

- Every answer in a simple letter cipher, so a glance cannot spoil the next case

- The full chain for each case: every clue and what it removed

- Numbered pages throughout

FOR the reader who likes the elimination-mystery idea but does not have three months, and would rather solve twenty-one crimes than one.