Unaccountably, MGM's excellent Nick Carter movies became the shortest series of detective films on record. The Carter films took the middle ground somewhere between the serial-like Brass Bancroft pictures and the sophisticated semi-comedy mysteries like the Thin Man films. The Carter series were fast-paced with quite a bit of action, but with some hilarious humor too. Bartholomew the Bee Man was the most unique of all detective sidekicks--quite loony, but very helpful at the same time. The interaction between Donald Meek's Bartholomew and Walter Pidgeon's self-assured Nick Carter was the best part of the series, which had several other things going for it too.
This final Carter film is a lot of fun, with Nick (unwillingly, at first) taking on a ring of Fifth Columnists (since this was filmed before the US entered the war, we're not told the villains are Nazis, but it's pretty clear anyway). Of course, the helpful and persistent Bartholomew is at his side--much to Nick's irritation. To further complicate things--and to make them still funnier--Joyce Compton is along for the ride too, as a delightfully brainless "detective" named Christine Cross. The plot gives us a new twist on the locked-room murder mystery: this time, a murder takes place in a locked airplane compartment! Karen Verne plays a German refugee suspected of the mysterious murder, and it's up to Nick to clear her--and protect her from the real killers, who are out to remove her at all costs. As in the first Carter film (NICK CARTER, MASTER DETECTIVE) there's a mastermind whose identity is not revealed right away, and an assortment of sinister henchmen. While trying to figure out the mystery (the who-dun-it isn't hard, but the "how dun it" certainly is) look for some great supporting players, including Chill Wills, Grady Sutton, Edward Ashley, and Tom Conway, soon to become a well-known film detective himself--the Falcon.
Be sure to check out this movie and the other Carter movies, NICK CARTER MASTER DETECTIVE and PHANTOM RAIDERS. All three are shown on TCM from time to time, and I highly recommend them.