) is a murder mystery novel written by Anthony Berkeley Cox
, using the pen name
Francis Iles. It involves a Devon
physician who slowly poisons his domineering wife so that he may be with the woman he loves. It is an early and prominent example of the "inverted detective story
", invented by R. Austin Freeman
some years earlier. The murderer's identity is revealed in the first line of the novel, which gives the reader insight into the workings of his mind as his plans progress. It also shows how the crime is investigated and how a case is developed by the police to the point of prosecution.
The novel was adapted as a four-part television mini-series by the BBC in 1979. This version was later featured in the U.S. PBS series, Mystery!, introduced by Vincent Price. Another adaptation was produced by Granada Television and broadcast on ITV in 2005. It, too, has been shown on Mystery!.