In the wake of his father's death, Chaney began to appear in feature films, most notably as the tragically strong Lennie Small in the film version of John Steinbeck's Of Mice and Men (1939) and as The Wolf Man (1941) -- a role that would typecast him in monster movies for the rest of his life.
In fact, when he died on July 12, 1973, of liver failure, he was the only actor to have played all four of the classic movie monsters: the Wolf Man, Frankenstein, Dracula and the Mummy.