At a very swank apartment in Boston, a husband is planning on surprising his wife for their anniversary. His TV turns off for no reason, then his lights shut off. We see a shadow on the wall behind him. Suddenly, that shadow appears in front of him and charges him His wife comes home to find her husband, Randy, sitting lifeless on a chair. She reaches out to touch him but he turns to dust in front of her eyes.
Agent Olivia Dunham and Walter and Peter Bishop are called to investigate Randy's death. Agent Phillip Broyles arrives on the scene, and says that he has seen this kind of killing before - four years earlier in Washington, DC. Broyles says that the man suspected in the killings in DC called him, distraught, and offered to turn himself in if the authorities could figure out his formula - a formula he said would stop the killings. They couldn't, and he killed two more people. Peter takes the formula to Walter in hopes that he can solve it.
In Boston's Latchmere General Hospital, we see the same shadow man sneak past a nurse. Broyles believes that the hospital is key to the killings and the FBI sets up shop. The shadow man slips past them and turns a patient into dust. The FBI names the suspect - a night nurse named Koslov. They storm his apartment but he is long gone. However, it is clear that he had been building something.
That something may be of grave importance. Agent Broyles is contacted by a former colleague, Senator Van Horn, who tells him that the CIA and the Department of Homeland Security are going to take his case from him. Apparently, Koslov is at the center of a Russian investigation for stealing materials from Russia. Broyles tells Dunham not to document anything about the case: he does not intend to give up the case.
Senator Van Horn sends Broyles some classified information. The object Koslov stole from Russia was not an object at all, but his comatose, Cosmonaut brother. Broyles and Dunham deduce that Koslov is moving his brother from coma ward to coma ward and suspect that he is still inside Latchmere. Inside the coma ward, the power suddenly shuts off. The nurse that goes to check on the patients is confronted by Koslov, who says he needs to disconnect a patient - presumably his brother. He knocks out the nurse and steals away in a hospital van with his comatose brother. He sets his brother up in a hotel, connected to several batteries. When the shadow tries to escape, he uses the current to try and contain it. He fears that the shadow is getting stronger.
Walter determines that the shadow man is after people's radiation, and that all the victims had some kind of elevated radiation levels. He believes that the Cosmonaut may have picked up a shadow organism in outer space. The shadow man is the organism projecting itself out of the Cosmonaut. Walter tells Broyles that he can "dominate" the organism - solving the formula. He determines that the organism has bonded with the Cosmonaut - there is no way to separate the two.
Broyles relays this to Koslov, imploring him to turn himself and his brother in. However, the conversation is one-sided: Koslov has been turned to dust by the shadow. The team arrives on site and as Walter desperately tries to find a way to stress the Cosmonaut's body, they hear a girl scream. Broyles pulls his gun and shoots the comatose Cosmonaut in the head, pulling the shadow man back into the body. As the episode ends, Broyles is confront by a CIA agent who warns him off filing a report. The CIA creep hints to Broyles that they finished the job he started and killed the Cosmonaut.