Mayko Tran, NorBAC's bioinformatics researcher, notifies the team at NorBAC about a case of privately contracted civilians who have all returned from Iraq exhibiting a wide range of mysterious illnesses. Meanwhile, Carlos asks NorBAC to investigate multiple cases of hemophilia in a small community in Mexico, where a large multi-national laboratory is working on GMOs. Jill must defend her reputation as a top virologist when a research paper she published is refuted.

David and Jill make a trip to Colorado where a rampant SARS-like outbreak is occurring. David is in shock when he discovers that the outbreak is Spanish Flu, the virus he dug up in Nunavut. Racked with guilt, he walks into the path of a car and is sent to hospital in a coma before he tells anybody his fears. Mayko Tran heads to Colorado to try to find Patient Zero.

Carlos and David helped by a Cuban scientist called Eva Ramone look into a claim than an exiled Cuban is a victim of bio-terrorism. Bob being persuaded that Caroline's nephew, Glenn, is improving calls Simon Jessup to help him out.

David and Carlos are still investigating the poison that is affecting Charringa's lemon crops in Florida, before the United States decide to bomb Cuba. Jill, on the other hand, asks Mayko to contact all the other labs using the same stem cells from Korea to let them know a retrovirus is in that strain. Bob offers to verify all the steps one more time with her and see if her findings are correct. Simon Jessup finding that Glenn responds to all the stimuli suggests that he undergoes brain surgery.

As the investigation continues on the suicides in Arkansas, the team believes it is a chemical release by worms that is the cause. Owen is charged with criminal negligence for the death by overdose of a school girl.

Despite David's public statement that GMO fish has no bearing on some illnesses, the dad of a young boy is convinced that his son is ill due to eating a the mutant fish. When an entire squadron of national guard falls ill, bio-terrorism is suspected, the team must work on the case.

It seems that the retrovirus that Jill discovered in the Korean stem cells is responsible for the illness affecting the national guards, thus showing the retrovirus was reactivated. Meanwhile, kids are all coming down with a mysterious and deadly disease that Norbac has to stop.

The antidote created to cure the national guards isn't doing its job properly as the guards fall even more ill with another disease. Caroline, still investigating what Weston did, finds that the White House is mixed into it.