Based on a true story, He Walked By Night (1948) transcends its B-movie origins through a combination of crime-fighting realism and starkly stylish film noir visuals. Directed by Alfred L. Werker and an uncredited Anthony Mann for Poverty Row studio Eagle-Lion, the documentary-style voiceover narration and emphasis on Los Angeles police procedure, especially by Jack Webb's evidence expert, tautly builds suspense from the real-life (and then-newfangled) tools of police investigation, rather than from excessive heroics or emotionality. Cinematographer John Alton's deep focus shots, chiaroscuro nocturnal lighting, and oblique camera angles match the inner menace of Richard Basehart's intelligent and unbalanced cop killer, and they help orchestrate a climactic chase through the Los Angeles storm drain system that rivals the sewer sequence in The Third Man (1949). Part of a wave of 1940s semi-documentary crime movies that included progenitor The House on 92nd Street (1945), Kiss of Death (1947), and Elia Kazan's Boomerang! (1947), He Walked By Night inspired Webb to create his "just the facts, ma'am" Dragnet series on radio and TV.