Marci is a reporter for a little newspaper of her university. She is passionated by space and she is persuaded that the government hides aien's presence on our planet. With her convictions and despite the disapproval of her chief editor, the young woman inquires with the assistance of two friends : Slick and Jake. While they break-in a secret military base, they assist in the crash-landing of the Solaris shuttle. Contrarily to the public announcement of its disintegration during its return in the atmosphere, the spaceship, victim of a frightful and murderous incident, was diverted in the surroundings of the base.
Onboard, « Mother In Law », a spider on which was realized experiences in weightlessness, escaped and slaughtered the crew in a bath of blood. By attempting to come in assistance to any survivors, they discover bodies of astronauts atrociously mutilated. When the army arrives on places, corpses are taken away and all hints of the shuttle is deleted. It seems that the governmental forces, under the commandment of agent Gray, do not wish to spread the strange affair.
The three daring spies clandestinely crawl inside a military vehicle that drives them about thirty floor lower down the base. Delivered to themselves, they discover a laboratory containing monstrous fœtus, and other peculiarities. Powerless, they assist in the sudden birth of a huge spider that extracts from the body of one of astronauts of the Solaris mission.
Ahead the bellicose arachnid, Slick, Jake and Marci try to escape by using the rescue staircases and discover the access to the laboratory of the project « Mother In Law ». By questioning computers, they understand that the nightmare begun here, with the repeated injection of alien DNA in a spider. The Solaris mission consisted in reactivating the DNA in weightlessness state in order that it lays its eggs genetically modified.
Jake is bitten. Without any known antidote against the venom of the frightful beast, the boy will die in painful sufferings. Attempting to escape by one of the providentially open elevators, Slick and Marci must face the thing that has risen tenfold its volume. Slick will not succeed in escaping the murderess web of the spider cleverly woven in the pipe of the elevator.
In the collapse, Marci comes across the government agent John Murphy. Both must help one another to survive. John is allthemore decided to attempt a new chance with the girl, that his superior, agent Gray, in a real psychopath, ready to kill them to preserve the thing alive. Accredited with the security codes, the two fugitives leave the underground base and crush the thing under the elevator. But Marci and John are not at the end of their surprises…
Spoiler ! the end of the story is revealed below…
Back on the campus, the agent Gray, whom the two runaway thought was dead, is waiting for them. While a mutant spider begins to get out of his body, the man confesses the ultimate goal researched: the creation of an army of killers arachnids. The spider, that has enlarged as suddenly as it flowered, ravaged places, and the police cannot stop the monster that seems insensitive to bullets. The frightful beast directs to the palace of congress in search of a place to lay its eggs. Marci and John use a military helicopter to track the beast. On the roof of the building, Marci, suspended in the void, opens the fire on the beast thanks to a rocket loaded with uranium. The heroine, who put the danger apart, is now going to be able to reveal the world, the terrible scheme of the government experiments.