This highly interesting little film almost fits into all three categories, but still doesn't fully meet the requirements for any of them! Though to be honest, this first Kildare movie--without Kildare--seems to be more of a crime/thriller than any of the earlier films in the series; that is, it focuses more on the crime aspect.
Our favorite over-the-top curmudgeon on wheels investigates the case of a, by all appearances, nice, well-mannered young man who just happens to have the nasty habit of turning psycho at the drop of a hat...and ends up becoming the killer's target.
The whole cast does a nice job, though as I stated earlier, the serious plot is sometimes undermined by the comedic undertone.
This is the first film in the series after MGM kicked Lew Ayers out for being a conscientious objector during the war, and that's when the "Dr. Kildare" series became the "Dr. Gillespie" series. This first one is pretty good, and very suspenseful; the script also contains a classic Gillespie line: "I'm sorry to tell you, you're son's a mental case."