When Leonard Vole is arrested for the sensational murder of a rich, middle-aged widow, the famous Sir Wilfrid Robarts agrees to appear on his behalf. Sir Wilfrid, recovering from a near-fatal heart attack, is 'supposed' to be on a diet of bland, civil suits. But the lure of the criminal courts is too much for him, especially when the case is so difficult: Vole's only alibi witness is his wife, the calm and coldly calculating Christine Vole. Sir Wilfrid's task becomes even more impossible when Christine agrees to be a witness not for the defence but for the prosecution.