The episode begins with a man and his dog searching an abandoned building in the Amazon rain-forest. They uncover a vat of blue liquid in a sealed room and tip it over before leaving. the dog begins to bark at the liquid, and the man turns around to see another version of his dog, which attacks him. after the title sequence, H.E.A.T. is seen trying to feed Zilla Junior a seaweed-based fish supplement in place of real fish in order to provide job security for local fisherman. In the lower decks, Monique Dupre encounters Philippe Roaché who informs her that the laboratory of a French geneticist has been discovered in French New Guinea and that a treasure hunter had released a dangerous experiment that he would like H.E.A.T. to take care of. they arrive in South America 400 meters away from the lab and on their way into the jungle Monique feels they are being watched. They soon find the laboratory and Monique heads back to the ship for supplies. The rest of the team remark on how amazing some preserved specimens in the lab are. Nick Tatopoulos eventually finds some of the blue liquid and gives it to Elsie Chapman who identifies it as pure DNA and says that is could take the form of any living thing it pleased. Back on the ship, Monique is attacked by a dog who is soon morphs into a snake and begins constricting her. Nick scares the DNA Mimic away, but it soon arrives at the lab in Monique's form and demands to know what the team has learned. By going through old computer files, Randy Hernandez discovers that there are two DNA Mimic batches, one stored in the lab and one in a safe location. The Mimic encourages him to find it, which he soon does. He then venture into the jungle to tell Monique about it. He finds Nick and the real Monique and the three piece together what happened before being confronted by the Mimic. It runs away and the three split up. The Mimic attacks Monique, but she escapes to the lab and the group reforms. The soon turn on each other and must decide if the Mimic is among them. Mendel Craven reveals that the Mimic's DNA produced more heat than humans, and they all undergo a thermal scan that reveals that Elsie is the Mimic. It escapes again, and the group goes into the jungle to find the real Elsie. When they do, they realize that the hidden container is labeled "Y" and that the one in the lab was "X". Nick reveals that these are the chromosomal symbols for male and female, and as such the Mimic is trying to find the other barrel because it wants to find a mate. The group formulates a plan to stop it and are able to track it and N.I.G.E.L., whom it had stolen. They find them in the water, but are too late to keep N.I.G.E.L. from opening the container. It transforms into a giant fish, which attracts Zilla Junior who tries to eat it. Nick loads a special Harpoon with a chemical Elsie developed to destroy the Mimic, but when he loads it he finds that the Mimic has taken the form of Zilla Junior. As it dies it attacks the ship, but Junior disintegrates it with his atomic breath.
"What kind of twisted mind would intentionally create such a bizarre life-form?"
"Let's ask your parents!"
— Mendel and Randy discuss a preserved mutant hybrid