In this frothy screwball comedy, Guy Johnson (James Stewart) is a private detective who is dedicated to his job but still quite green and a bit of a bumbler. Guy is hired to keep a close watch on Willie Heyward (Ernest Truex), a footloose millionaire with a habit of getting into trouble. One night, Willie ties one on and somehow ends up accused of murder, with Guy also charged as an accomplice. After the two are convicted, Guy escapes from the train taking him to prison, and he hits the road in hopes of finding evidence that will clear both himself and Willie. En route, Guy encounters Edwina Corday (Claudette Colbert), an eccentric poetess, and essentially abducts her, forcing her to let him use her car and help him as he tries to find the real murderer. But before long, Edwina seems more amused by Guy than threatened, and she falls in love with him as he assumes a bewildering series of disguises (actor, driver, Boy Scout) while trying to find the truth before it's too late. It's a Wonderful World also features Guy Kibbee, Edgar Kennedy, Sidney Blackmer, and Hans Conried.