In the distant future, a genetic research station is located on the remote desert planet of Xarbia, and a research team has created an experimental lifeform they have designated "Subject 20". This lifeform was built out of the synthetic DNA strain, "Proto B", and was intended to stave off a galaxy-wide food crisis. However, Subject 20 mutates rapidly and uncontrollably and has killed all of the laboratory subject animals before cocooning itself within an examination booth. After Subject 20 hatches from its cocoon, it begins killing the personnel at the station, starting with the lab tech charged with cleansing the subject lab of the dead animal test subjects.
Professional troubleshooter Mike Colby, accompanied by his robot assistant SAM-104, is called in to investigate the problem. After Colby settles in, his decision to terminate Subject 20 to prevent further deaths is met with research-minded secrecy and resistance. The staff of the station includes the head of research, Gordon Hauser, his assistant Barbara Glaser, lab assistant Tracy Baxter, the station head of security and Cal Timbergen, the chief of bacteriology.
As Subject 20 continues to unleash a storm of gory fatalities that decimates most of the station crew, the lid on the deception is finally withdrawn: Subject 20's genetic design incorporates human DNA. Furthermore, its method of killing is most horrifying: this beast injects its prey with the Proto B DNA strain which then proceeds to remove all genetic differences within specific cells. The result is a terrifying death as the victim's living body slowly erodes into gelatinous pile of pure protein which subject 20 then uses for food. After its final mutation, where the creature evolves into a huge insect-like being with a large mouth full of sharp teeth, the creature is eventually slain when it eats Cal's cancer-ridden liver, its body genetically self-destructing from within. Mike and Tracy are the only survivors.