Babylon 5 The Lost Tales

Colonel Elizabeth Lochley calls in a priest, Father Cassidy, to come to Babylon 5 to help a maintenance worker, Simon Birk, who appears to be possessed. The entity possessing Birk wants to be released, and is trying to force Father Cassidy to exorcise him. Colonel Lochley figures out that the entity possessed Birk while he was on a visit to Earth, after which Birk had hitchhiked to Babylon 5.