Gosa estar muit conoixito por as suyas interpretacions de cintas de cine de terror, destacando-ne a suya interpretación d'o presonache de Frankenstein. D'entre a suya filmografía, cal destacar-ne cintas como Two Arabian Knights (1927, Lewis Milestone), Frankenstein (1931, James Whale), Scarface (1932, Howard Hawks), The Mask of Fu Manchu (1932, Charles Brabin), The Mummy (1932, Karl Freund), The Lost Patrol (1934, John Ford), Bride of Frankenstein (1935, James Whale), The Invisible Ray (1936, Lambert Hillyer), West of Shanghai (1937, John Farrow), Son of Frankenstein (1939, Rowland V. Lee), The Devil Commands (1941, Edward Dmytryk), House of Frankenstein (1944, Erle C. Kenton), Abbott and Costello Meet the Killer, Boris Karloff (1949, Charles Barton), u Frankenstein 1970 (1958, Howard W. Koch).