Jim Matthews (Eion Bailey) died in the S3 finale when MIY killed him. a moment that landed as the season's most brutal gut-punch. But FROM doesn't waste death. In S4, Jim's ghost (or something wearing his likeness) has been one of the show's most active presences: guiding Ethan to the basement door, warning Boyd about hidden structures, and driving action in nearly every episode. The question fans are debating is whether Jim's ghost is actually Jim, or whether MIY or the town itself is using Jim's image.
Split between: (A) Jim's actual soul is trapped and communicating, (B) the town or MIY has absorbed Jim and weaponized his likeness. The S4E5 basement sequence, where Jim's ghost explicitly led Ethan to danger, has shifted many toward option B.