An elderly and ailing barrister, Sir Wilfrid Robarts, takes on the case of Leonard Vole, a man accused of murdering a wealthy widow for her fortune. Despite his frail health and the advice of his nurse, Sir Wilfrid becomes intrigued by the case's complexities and Vole's insistence on his innocence. Central to the defense is Vole's alibi, which hinges on the testimony of his enigmatic German wife, Christine. However, as the case progresses, Christine's unwavering demeanor and conflicting statements cast doubt on her loyalty and honesty.

In a shocking twist, Christine is called as a witness for the prosecution instead of the defense, asserting that Vole confessed to her about committing the murder. Her testimony delivers a devastating blow to Vole's case, and the courtroom drama intensifies as Sir Wilfrid navigates through the intricacies of her statements. He faces numerous challenges in discrediting her account, all while grappling with his own declining health. The resulting courtroom battles reveal deep-seated motives and intricate deceptions as Sir Wilfrid works tirelessly to uncover the truth and ensure justice is served.