It’s one of the scariest horror movies ever. (Go ahead, say it’s not. We dare you.) The filming conditions were equally frightening. As author Jason Zinoman relates in his new book on American horror films, Shock Value, director Tobe Hooper put his cast through hell. And it was mostly due to the heat typical of a Texas summer. “It was shortly after dawn on July 15, 1973, when the filmmakers gathered for the first time at an isolated farmhouse in central Texas, dressed in T-shirts and jeans,” writes Zinoman. “It was around 100 degrees … The cast worked sixteen-hour days and spent much of the time covered in Karo corn syrup … and real bruises. Cattle bones were strewn all over the unventilated room. Everyone was miserable.” And it shows. The film is oppressively dusty and hot, and the cast members glisten with sweat, frustration and fear. Appropriately, Hooper’s film ends with the monstrous Leatherface and his chain saw doing a beautiful pas de deux while silhouetted in the scorching setting sun.