The team investigates a missing woman's boyfriend, with whom she lived. However, they determine that he has a twin brother and quickly turn their attention to him.

When a homeless woman disappears from a shelter, the team is forced to re-examine the case of twin brothers Greg and Rick Knowles. Five months earlier (Doppelganger), Greg Knowles had confessed to a series of brutal murders, but the team was always convinced that it was Rick who had actually performed the killings. When Greg is released from jail and exonerated of the crimes, the team has to work against the clock to prove that Rick is the guilty party and to save one twin from the other.