Batman Arkham Asylum Episode 4: Patient X

"Batman catches a glimpse of the Scarecrow and several unfortunate victims of his fear gas trapped in an operating room. Soon he is affected by the gas himself, first subtly then in increasingly surreal ways."
"Joker challenges Batman to make it undetected past four of his henchmen patrolling the room; if he is spotted Harley will execute Gordon instantly. If he succeeds, the Joker directs his attention to a surprise left for him in a previously locked chamber in the middle of the room."