Black Coffee. Hercule Poirot. Book 7,5

Sugar and cream? Or a lethal dose of poison?

The inventor of a powerful new explosive,Sir Claud Amory, is somewhat disconcerted when the chemical formula goes missing - the situation worsened by the knowledge that the thief is one of Sir Claud's house-guests. A relative? Or a 'friend'? Whoever the culprit, Sir Claud decides to give them a sporting chance - which is more than someone gives him. As the doors are locked and the lights turnede . . .Adapted as a novel by Charles Osborne