Bill Summers (John Archer), his valet Jefferson Jackson (Mantan Moreland) and the pilot James "Mac" McCarthy (Dick Purcell) are flying to the Bahamas on a top secret government mission when their plane gets into trouble over a remote Carribean island. They are forced to crash land, but not before picking up a mysterious transmission over the radio. The island is apparently deserted until the party discover a mansion in the jungle, and ring the doorbell; there's no reply, so they enter the darkened building, only to be greeted by a gaunt figure walking down the stairs towards them...
King of the Zombies is basically one spooky scene like that after another, and was scripted by Edmond Kelso. It was inspired as a cash in on the then-popular run of horror comedies, and as such prominently features Moreland as the comic relief, doing his accustomed frightened manservant act. And it's to the film's benefit that he does, as it would be a sepulchrally dry experience otherwise - Archer and Purcell are wooden heroes, and when they meet the villain of the piece, the monotonous Doctor Mikhail Sangre, played by Henry Victor, you'll wish the first choice for the role, Bela Lugosi, had been available.
The action moves at a snail's pace when Moreland is offscreen, and as he's smarter than his companions, it can be frustrating to watch them dismiss his warnings and be one step behind Jeff, who twigs right away that the Doctor is up to no good and that the house and its surroundings are inhabited by zombies. The movie zombies of the thirties and forties were not the flesh-eating animated corpses of the George A. Romero efforts, but people under the spell of voodoo. Here, the Doctor is obsessed with hypnotism, and has a somnambulistic wife who he is trying to revive - which doesn't have anything to do with the rest of the plot.
Jeff may be smart, but he's treated like one of the servants by the Doctor: when he pours a brandy for his newly arrived guests, he doesn't pour one for Jeff, and expects him to sleep in the servants' quarters instead of with Bill and Mac. This gives Moreland more opportunities to play off the staff of the house, in particular the maid, Samantha (Margueritte Whitten), who says she is from Alabama, and acts as a straight woman for his routines. In truth, although his manful efforts go some way to brightening up a lifeless chiller, Moreland doesn't enjoy enough funny lines, and relies too much on looking scared for laughs.
King of the Zombies has a reputation for being one of the better Monogram horrors, but it doesn't really deserve it. The plot stumbles like the undead from fright scene to comedy set up, and the villain's plans are fuzzily thought out. One interesting aspect is that he's not concentrating on voodoo for his zombies, he's using a Druid version of it, from Mac's native Ireland, and he even turns Mac into an Irish zombie. Eventually a story about a kidnapped admiral arises, and the Doctor, who claims to be a refugee from Austria, is revealed as a spy. Not funny enough and not creepy enough, the film is a mere shadow of its influences, with a thrown together appearance. Music by Edward Kay (which, oddly, was nominated for an Oscar).