Curtis Rollins is dying in ER from gunshot wounds after going to a scene without backup, when Axon simultaneously sees him walk out of the hospital.
Elsinger questions Axon, Donahue and Constantine about the entire thing, and it transpires that Rollins ws immersed in the White Crow Killer case.
Axon sees Rollins again in the street the next day, even though he's simultaneously lying in hospital, and pulls the security tapes from the hospital of the night before. Rollins is clearly shown. Elsinger assigns Donahue to help Doyle, Donner and Hendricks investigate, and sends Axon and Constantine to work on another case.
Under hypnosis, Rollins recalls a doctor healing him in ER, but taking something from inside him that he shouldn't have. The duplicate seems to have taken Rollins' knowledge of the White Crow Killer and taken over from him.
The duplicate kidnaps the doctor, and the team captures the duplicate, but don't find the doctor. The two Rollins meet and talk, and the two Rollins become one, once more, and he locates the doctor.