The plot centers on the confusion surrounding the uncanny resemblance of a mild-mannered advertising clerk, Arthur Jones (Robinson), to escaped convict "Killer" Mannion. After the police mistakenly arrest the clerk, they give him a passport to avoid repeating the error.
As a novelty, newspaper man Healy (Wallace Ford) hires the clerk, an aspiring writer, to do a series on his impressions of Mannion. But later, the convict appears at Jones' apartment and demands the passport for his own protection, threatening the fearful clerk if he reveals anything about his visit. The criminal also orders Jones to write the series of articles based on his reminiscences, which alerts the police that something strange is going on.
Although the district attorney finally places Jones in jail under protective custody, for his safety, Mannion switches places with him in order to kill another inmate.
Special Notes: Lucille Ball has a small uncredited part as a bank employee, and Francis Ford, director John Ford's older brother, appears as a newspaper reporter at the dock.