 Edward Wain (Robert Towne) is inept Government Agent XK342. He is on the trail of mobster Renzo Capeto, a Bogart wanna-be who is transporting Colonel Tostada, a group of exiled Cuban nationals, and a large portion of the Cuban treasury out of Cuba. Renzo is also accompanied by Mary-Belle Monahan (an infamous gangster moll), Happy Jack Monahan (her dim-bulb gangster-in-training brother) and Pete Peterson Jr. (a hoodlum/animal impersonator). Wain assumes the identity of "Sparks Moran" and somehow convinces Renzo to add him to the gang. Renzo concocts a plan to "invent" a sea monster, so that the Cubans will allow him to change their course. The phony sea monster will allow him to eliminate a few of the Cubans, and get himself closer to the treasure. Unfortunately, someone else invented the monster first.