The Walk-in - S2-E17
Continuity mistake: When Jim brings a new body to the morgue there's a "John Doe" already lying there, and in the close up we see that the corpse's right foot is missing the middle toe. We see this again later when Jim's ring is stolen from his locker, with the bloody right footprint on the floor. However, when Melinda shows up the close-up shots of the bloody footprints have been flipped so it's the left foot with the missing toe, but what's funny is that in the audio we hear Jim say, "The middle toe is missing on the right foot."
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