The Crime Scene in Season 4, Episode 2: “Heroes and Villains”
When an ex-con is mysteriously slain in an alley, Castle (Nathan Fillion) and Beckett (Stana Katic) believe a vigilante is behind the murder. But efforts to identify their suspect are thwarted when they discover that he roams the city in a Superhero costume — and may indeed be a Superhero. Can they capture and unmask the killer before he strikes again?
Original Air Date: September 26, 2011, 10/9c