An amateur detective organizes his Crimes Circle to investigate the death of Mrs. Bendix, who dies after receiving poisoned chocolates; with Scotland Yard having stalled its inquiry, members pool expertise, reconstruct events, scrutinize alibis and motives, and propose competing solutions. The story unfolds as a locked-room style puzzle emphasizing logical deduction, group debate, and careful forensics, proceeding through clue-driven chapters and a dramatic denouement that reveals how the poisoning occurred and why, while intentionally inviting readers to weigh alternative explanations.