Rosalie van Beer is a widowed, childless woman who comes into money when all the relatives of her late husband unexpectedly die in a plane crash.

She moves into the house in Devon that was built by her father-in-law and leads a quiet life there with Philip, a sickly child for whom she engages a private tutor.

The situation escalates when van Beer takes away Philip's pet rabbit, which he called Sredni Vashtar (the name of a weasel in a Saki short story, which kills a cruel aunt), and gasses it in the kitchen.

Accordingly, he begins the novel by giving short biographies of each juror in which he describes their individual experiences, their social and financial background, the outlook on life which each of them has acquired over time, and also any possible predisposition to judge others harshly.

Postgate presents all these factors to show that they prevent the jurors from considering evidence objectively, and that they will respond to the case emotionally rather than realistically.