On a fine autumn weekend Lord Aveling hosts a hunting party at his country house, Bragley Court. Among the guests are an actress, a journalist, an artist and a mystery novelist. The unlucky thirteenth is John Foss, injured at the local train station and brought to the house to recuperate - but John is nursing a secret of his own.Soon events take a sinister turn when a painting is mutilated, a dog stabbed, and a man strangled.