A New Yorker mysteriously turns ill in the middle of the street. Dr. Stephen Connor has to quit his son's baseball game and go to work with his NIH team to find out the cause of this situation and to find a cure before it's too late. Meanwhile, Dr. Miles McCabe is assigned to a hospital in Richmond, Virginia to investigate strange bruises on a baby.
Four teenage girls are struck with encephalitis. The NIH is summoned to fine the cause and the cure before time runs out. However what's thought to be STD (Sexual Transmitted Disease) wasn't what it appears to be and a pair of pants holds the key to the truth.
Dr. Connor and company are summoned by the US Army to investigate four Gulf War soldiers who recently came back with a lethal pulmonary disease. Powell believes it's Gulf War syndrome, until Connor finds out that several old citizens who haven't gone to war, also have it too.
Dr. Connor, Miles, and Frank are summoned to a Bahama resort to investigate why adult vacationers are starting to fall ill. But when the children also start to fall ill, the team realize they don't have much time left. Meanwhile, Durant and Rossi are in Miami to investigate an illness of an old man.
The team is split up to investigate two different cases. Connor, McCabe, and Powell are summoned to a Caribbean resort to investigate adults with a strange respiratory problem. Meanwhile, Durant and Rossi stays in Miami to investigate an illness of an old man.
When several girls at a Midwestern College fall ill to a deadly disease, Dr. Conors and his team are summoned to find the cause. The team will soon find out these girls are not suffering from the same disease and a lipstick holds the answer to all the riddles.
A woman faints during her bridal shower. Dr. Stephen Connor and his crew travel to Philadelphia to investigate as more patients rush in the medical center. As the team try to put puzzle together, they realize they got a case of anthrax at hand.
The NIH is summoned to a small town in Virginia, where some people in a small town is infected with a strange virus. Struggling to find out what that virus is, more and more people are checking in the hospital with the same virus. Can Dr. Stephen Connor and his team find the true identity of the virus and the antibiotics in time before the entire town is infected?
A little girl has fallen ill and needs a healthy bone marrow. However, her adopted parents recently died due to an identical aplastic anemia. As the NIH tries to find out the source of this illness, Eva Rossi must find the right bone marrow transplant from her biological parents before it's too late.
Several females check into a LA hospital after fallen ill due to a deadly disease. The NIH is summoned into the scene and are ask to find the cause and a cure. Their commonality? They all are adult film actresses, so the team immediately thinks some kind of STD or HIV are involve. But when the test comes back negative for those disease, the team has to search elsewhere for the answer.
Several patients have mysterious infected bateria on them after having surgery. It's up to the NIH to stop this "Angel of Death", who also has a past that no one should be proud of.
Several people are struck with a disease that Dr. Connor and his team have no clue on what it is. They suspect the disease are being transfer from seals to humans. The team swipe the beach clean, but find nothing. Frank Powell retrieve some garbage that floated ashore, thinking that it's the waste that is infecting the seals and humans. But the results also come back negative.
Several people in a Montana camp resort got infected with a disease, presumably smallpox. Dr. Stephen Connor and the NIH are summoned to the scene to try to stop the spread of the disease. But when the FBI show up, there is indication that this may be a terrorist's plot to spread the disease.
Several people in a station in Antarctica are getting infected with an aggressive ammonia. What's even worst is one of the NIH's own is also infected and the team may have difficulty getting aid because of a strong storm outside.
A plague outbreak is discovered near Baltimore. While the NIH tries to find the source and stop it from spreading. Along the way, they find some dirty cops trying to cover up a murder. Viewers also get a glimpse on Dr. Stephen Connor's past.
Dr. Stephen Connor splits the team into two. Miles McCabe and Eva Rossi investigate a case where several soldiers' wives are all having strange miscarriages. Connor, Natalie Durrant, and Frank Powell investigate why some patients are having a strange defect that in their legs.
In a rare crossover with several casts of Third Watch, Dr. Stephen Connor and his team heads to NYC to uncover a multiplying virus before it spreads anymore. Stephen teams up with the NYPD to find patient zero, the one who is carrying the disease and spreading it around the city.
Two politicians and a cop are infected with what is first suspected as a STD (Sexual Transmitted Disease). But this strange disease is killing patients at very fast rate and Dr. Stephen Connor and Co. must find the source of this virus as fast as they can.
An outbreak occurs in Mexico and the NIH sent several teams there to help with the relieve effort and to find the source of this disease. When they lost contact with Dr. Natalie Durant, Dr. Miles McCabe, Eva Rossi, Dr. Stephen Connor and Frank Powell decide to travel to the there themselves to help find them.
As Dr. Natalie Durant continues to try to find what kind of disease they are dealing with, Dr. Stephen Connor is at church Mission La Roca trying to rescue Dr. Miles McCabe and his patients to the hospital before the church collapses.