In the heart of Mexico, a team of archaeologists led by Dr. John Fielding embarks on an expedition to uncover the mysteries of an ancient Mayan civilization. They stumble upon the remnants of a lost city, where they discover a vast underground chamber adorned with artifacts and carvings that suggest a sudden and mysterious demise of its inhabitants. Among the relics, they find a pool filled with a dark, viscous substance. Their curiosity leads them to retrieve a statue of Caltiki, a goddess associated with doom and destruction. As they investigate further, one of the members is drawn to the liquid and inadvertently disturbs it, releasing a monstrous entity.

The amorphous creature wreaks havoc, forcing the team to flee back to their base with samples for further study. Dr. Fielding and his colleague, Dr. Max Gunther, attempt to understand the creature's origins and weaknesses. As they delve deeper into the research, they begin to suspect a correlation between the monster's behavior and celestial events, specifically radiation from a comet expected to pass close to Earth. With time running out, the team grapples with how to contain or destroy an enemy that seems impossible to defeat, unaware that their every move may be sealing their fate. The tension mounts as they race against both their own ignorance and the relentless advance of the creature.