Other mistake: When Rick suggests that the ghost may have had multiple personality disorder and that's why he's appearing as different people, Melinda says this isn't possible, because when someone dies they're free from all afflictions they had when they were alive. In season 2 episode 4, "The Ghost Within", the featured ghost has autism and is not able to verbally communicate or make eye contact with Melinda and we never see him freed from this mental affliction.
Other mistake: The show was supposed to be on the East Coast, however you can see a reflection of a California Flag in Melinda's front windshield. (00:09:35)
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