He Walked by Night (1948) is a seminal film noir police procedural that tracks a desperate manhunt through Los Angeles. Inspired by the real-life crimes of Erwin Walker, the story follows Richard Basehart as Roy Morgan, a cold-blooded, tech-savvy killer who evades capture by monitoring police frequencies. Directed by Alfred L. Werker and an uncredited Anthony Mann, the film is renowned for John Alton’s stark, atmospheric cinematography, culminating in a legendary chase through the city’s sewer system. Crucially, actor Jack Webb was so inspired by the film’s realistic forensic focus that he created the iconic franchise Dragnet shortly after.