An urgent call from physicist Sir Claud Amory sends detective Hercule Poirot rushing from London to a sprawling country estate. Sir Claud fears a member of his own household wants to steal a secret formula destined for the Ministry of Defense. But Poirot arrives too late. The formula is missing. Worse, Sir Claud has been poisoned by his after-dinner coffee. Poirot soon identifies a potent brew of despair, treachery, and deception amid the mansion's occupants. Now he must find the formula and the killer...while letting no poison slip 'twixt his lips.