Batman: The Animated Series

Season 1

Episode 19: Fear of Victory

Several sportsmen start receiving strange letters in the mail, and having frightening hallucinations at their next game. At the same time, one man is making thousands of dollars betting on the events. Batman and Robin (the latter of whom becomes infected), start their own investigation, and come to the conclusion that someone else is continuing the Scarecrow's crimes, since the Scarecrow is currently locked up in Arkham Asylum. Or isn't he?