Character mistake: When Aiden and Melinda go the the hospital to visit Jim/Sam the picture on the hospital badge is of Jim Clancy not Sam Lucas... Jim has been in Sam's body for many years at this point. You can see the badge multiple times in the episode.
Character mistake: Jim is at the hospital - at the end of his phone conversation with Melinda, someone calls out "Dr. Clancy" when the character is Sam Lucas. (00:09:15)
Other mistake: In the scene immediately after the opening credits, Jim is talking to Melinda on the phone. Right as he's hanging up, someone calls out "Dr. Clancy? Got a minute?", to which Jim waves in acknowledgement and starts up the stairs. (Jim's spirit has been in Sam Lucas' body since season 4 and in an earlier season 5 episode, his white coat is embroidered S. James Lucas, M.D). (00:09:15)
Continuity mistake: After Jim and Aiden surprised Melinda with the new SUV Melinda drives off in the red vehicle, but when Aiden and Jim do their fist bump it cuts to a closeup of Jim, and the red SUV is still parked beside Jim.
Answer: This "spirit" appears in several episodes throughout the rest of the season including the season finale. He's a "bad spirit" that is intent on keeping souls trapped on Earth. With the death of Andrea (her business partner) he wanted to make a deal with Melinda, to give him HER soul to release everyone else including Andrea to cross over.
Boobra