How did beloved movie dogs become man-killers like Cujo and his cinematic pack-mates? For the first time, here is the fascinating history of canines in horror movies and why our best friends were (and are still) painted as malevolent. Stretching back into Classical mythology, treacherous hounds are found only sporadically in art and literature until the appearance of cinema's first horror dog, Sherlock Holmes' Hound of the Baskervilles. The story intensifies through World War II's K-9 Corps to the 1970s animal horror films, which broke social taboos about the "good dog" on screen and deliberately vilified certain breeds--sometimes even fluffy lapdogs. With behind-the-scenes insights from writers, directors, actors, and dog trainers, here are the flickering hounds of silent films through talkies and Technicolor, to the latest computer-generated brutes--the supernatural, rabid, laboratory-made, alien, feral, and trained killers. "Cave Canem (Beware the Dog)"--or as one seminal film warned, "They're not pets anymore."