M is a 1931 German crime film directed by Fritz Lang and written by Lang and his wife Thea von Harbou. M was Lang’s first foray into sound film although he had directed over a dozen films previously including Metropolis. Over the years the film has become a defining classic that rivals Lang’s other works for the title of “magnum opus”. Lorre was type cast for years after the film’s release as a villain for his portrayal of a child murderer (and, it is implied, a pedophile). M also pioneered the use of leitmotif to give the film score a more intense feel.