Andrew Basnett, retired botany professor, accompanies an old friend, whose sister has received a blackmail letter, to her home in a Berkshire village. The letter had obviously been put in the wrong envelope, but it seems to indicate that a murder has been committed in Lindleham, where, strangely, several people are missing.

But as Andrew quietly investigates the neighbours, the realisation dawns that his friends, too, have something to hide.