After a surfer and a female volleyball player fall ill to a deadly mysterious disease in a seaside town, Dr. Connor and his rapid-response team fly in and soon begin to wonder if the increasing number of human victims are related to the deaths of nearby seals -- which could result in a sanctioned slaughter of the mammals. But an idealistic local doctor (as Karen, guest star Marguerite MacIntyre) fights to protect the seals and forms an appreciative bond with the unmarried Connor -- until she too begins to show frightening symptoms of the spreading sickness.

Dr. Connor and his elite medical experts chopper into a frozen Arctic scientific station to probe a deadly brain affliction that climaxes when its victims fall into dementia. As a whiteout snow storm strands some of the team on the tiny base camp, Powell begins to display the same frightening symptoms. As a weakening Powell conceals the news from his family back home, Connor is sure that the source is a bacterial or fungal infection -- but the window of time to prove his theory is rapidly evaporating.