Horace Manning, scientist, recluse and ‘closed book’ even to his friends is found dead in his study at 4am, following a dinner in honour of his daughter Helen’s engagement. An ivory-handled carving knife rests between his shoulder blades as the houseguests gather about to witness the awful crime. The telephone line has been sabotaged; a calculated murder has been committed. Rewinding twelve hours, the events of the afternoon and evening unfold, along with a multitude of motives from a closed cast of suspects and clues until the narrative reaches 4am again – then races on to its riveting conclusion at 4pm.