In “Lazarus,” the fifteenth episode of the series, Scully’s ex-boyfriend and fellow agent, Jack Willis (Christopher Allport) is killed during a stakeout of a bank, though afterward the robber is shot by Scully.
Both men momentarily die, though upon the resuscitation of Agent Willis, somehow the consciousness of the robber is transferred to his body. after which his body is occupied by the soul of the robber.
It’s not the best of the series, mainly because has a tendency to break its own rules. For instance, there’s a moment when a tattoo transfers itself from the wrist of the thief, to that of Agent Willis.
It’s visually an interesting conceit, but not to necessary to get across the point that the agent was no longer himself.