They find the deserted patrol boat covered in a strange slime; the jumper's body then floats to the surface, now blackened and drained of bodily fluids.

Twill takes a sample of the slime to the base lab for analysis, where he teams up with recently widowed Gail MacKenzie and Dr. Jess Rogers.

The molluscs escape into an irrigation canal system, attacking livestock, a lock keeper, a trysting couple, and others.

He arrives and finds that the hatched mollusc has Gail and Sandy cornered in a closet, where they ran to escape from the monster.

He fights it with laboratory chemicals, a CO2 fire extinguisher and a live steam line until other Navy personnel arrive and shoot the mollusc.

The story for The Monster That Challenged the World came from David Duncan, who also went on to pen screenplays for The Time Machine (1960) and Fantastic Voyage (1966).

[7]A TV Guide review of The Monster That Challenged the World noted, "Fine special effects help this film along by adding an atmosphere of impending danger.

"[8] A later review by author Dave Sindelar of Fantastic Film Musings and Ramblings remarked: "For some reason, this fifties monster movie doesn't get much respect, but I think it holds up extraordinarily well.

For one thing, I think the characters are unusually well drawn for this type of movie, and they're given a dimension and a sense of realness that adds a lot to the proceedings".

[11] Kino Lorber's Blu-ray release of the film features an audio commentary by Tom Weaver, Dr. Robert J.