The Return Of Doctor X (1939)

Starring Humphrey Bogart, Rosemary Lane, Wayne Morris, Dennis Morgan, John Litel
Directed by Vincent Sherman
(actor & director credits courtesy IMDB.com)

When a newspaper reporter loses his job after mistakenly reporting a famous starlet dead, he recruits a doctor to help him discover the truth, and are led to a blood specialist and his sinister assistant.  

Humphrey Bogart's only horror film, which I've heard was a "punishment" levied on the actor by his studio's bosses, need not be looked at a low point in the dramatic actor's career, as I feel it's a gripping and enjoyable movie.  The cast is well worth watching, with Bogart joined by Wayne Morris in an entertaining performance as the glib reporter, a young Dennis Morgan as the noble but inquisitive doctor, and John Litel, who is underrated as the mysterious Dr. Flegg.  Huntz Hall, better known for his dimwitted persona in the East Side Kids and Bowery Boys movies, even shows up as an office boy at the newspaper.  Although Bogart's character is key to the story, the actor is essentially playing a supporting role here, but strikes the right eerie notes, with a creepy vocal delivery and a menacing walk.  Although Warner Brothers didn't venture into the horror genre often, they clearly looked at rival studio Universal for a template for their film, with a screenplay that calls upon elements of both Frankenstein and Dracula, and a Bride Of Frankenstein-like white streak through Bogart's hair.

The Maltese Falcon (1941)

Starring Humphrey Bogart, Mary Astor, Gladys George, Peter Lorre, Barton MacLane
Directed by John Huston
(actor & director credits courtesy IMDB.com)

Detective Sam Spade is hired to rescue a woman's sister from a criminal, but soon discovers he's been used as a pawn by a group of ruthless characters after a priceless statuette.

Humphrey Bogart makes quite the impact as Dashiell Hammett's private eye in this version of his famed novel, supported by quality turns from Astor, Lorre, and the unforgettable Sydney Greenstreet.   It's not hard to see how this role showcasing Bogart's toughness, intelligence, and humor launched him on the road to stardom, and marked the start of an equally fine career for his director John Huston, who delivered a stylish and entertaining mystery.  Not to be neglected is the excellent dialogue throughout the film, advancing the story and enriching each character.  Perhaps the film's only detriment, albeit a minor one, is the casting of Astor, who despite delivering an excellent performance, is not the knockout beauty that the screenplay describes her as.