David Graham (Michael Redgrave) is an alcoholic father who arrives in London after his release from an American sanatorium. His son has been sentenced to hang the next morning for murder, and Graham's lawyer, (Peter Cushing), stresses that they have just twenty-four hours to save him. Convinced of his innocence, Graham tries to unravel the twisted connections that his son had with the Stanford family and the murdered girl. But Graham's unwelcome interference drives the Stanfords apart and Robert Stanford (Leo McKern) forbids his wife (Ann Todd) from helping. As time ticks away and a last minute reprieve fails, Graham must battle his alcoholism, Robert Stanford and the entire British legal system if he is to save his son from the gallows.