This sparkling mystery novel reveals a sensational new discovery in the field of scientific criminal investigation... It all began with an auction. If Perry Mason hadn’t made a casual, five-dollar bid he wouldn’t have bought the personal effects of Helen Cadmus, missing secretary presumed a suicide... If the personal effects hadn’t turned out to be diaries and a photograph album, Benjamin Addicks wouldn’t have come into the picture... If Benjamin Addicks hadn’t been an eccentric millionaire, he wouldn’t have been conducting psychological experiments on gorillas... And that brings us to the most spine-chilling scene ever encountered in a Gardner mystery: Perry Mason creeping through a silent house, stalked by A MURDEROUS, GRINNING GORILLA!