A satellite crashes near the small town of Piedmont, New Mexico, and a recovery team discovers that nearly all the residents have died due to a mysterious illness. The U.S. military quickly quarantines the area and assembles a team of top scientists to investigate the cause of the deadly outbreak. Dr. Jeremy Stone and his colleagues are brought to a high-tech, underground laboratory known as Wildfire, specially designed for biological research and containment. The team discovers that the lethal agent is an extraterrestrial microorganism code-named Andromeda.

As the scientists race against time to study the organism, they find it's capable of rapidly mutating and adapting to its environment. Two survivors from Piedmont—a baby and an old man—offer crucial clues that may help understand Andromeda's behavior. The team members face numerous technical and personal challenges as they work to find a solution before the microorganism can spread further and cause a global catastrophe. The stakes are heightened by the lab’s automatic nuclear self-destruct mechanism, which poses an additional risk should containment fail.