Mysteriously, the Martian exploration probe Viking 2, whose contact was lost since 1983, is discovered in the desert of Mojave. The probe is transported in a space research center near. The Dr. Square Montgomery and the space biologist Gracia Scott, both working for the NASA inquire on the strange appearance. The hoax is rapidly put apart and the two scientists begin to work on the incredible discovery. How Viking 2 could have travel back to earth by its own?
Their researches turn out when the army, under the commandment of the Colonel Jessie Pratt invests the research center and dismiss the two scientists of the inquiry. But, while Case and Gracia refuse to leave, a strange phenomenon produces. A biological creature extracts from one of the compartment of the probe and escapes in the corridors of the center. Ahead the gravity of the danger, the place is quiclky put in quarantine with order to fire on any person who would attempt to exit.
Inside, the two civilians and a handle of soldiers must find back the thing and stop it at any costs.
The alien hunting begins but this one makes victims. Contrarily to Dr. Gracia Scott's advice, the question is now not to catch the entity but to kill it. Endowed with an extreme intelligence the thing has in addition taken superhuman dimensions. After a long hiding party, the entity is found beside the probe that swallows the maximum of space and military informations from the NASA and the defense.
Soldiers have no other choice than shooting at the creature and killing it. The alien is dissected by the biologists so as to learn more about it and to verify that it does not hold any infection that could put in peril the humanity if it spreads. It is elsewhere to watch for this principle to be respected that a bomber holding an atomic bomb is ready for intervene in case of a breach in the rule. The raising of the quarantine seems repelled when the autopsy reveals the presence of a king of egg in the alien's entrailss that nestes...
Spoiler ! the end of the story is revealed below…
A new hunting for the alien is engaged but this one is bloodiest. To finish, the visitor escapes the space research center and the threat to bomber the center and its close region is put to execution. Is the hypothesis that extra-terrestrials went to ask to put an end to Martian incursions verified when a new probe is signalled entering the atmosphere?