Despite Dean's directive to forget about looking for a cure for the Mark of Cain, Sam continues to do research. Dean suspects Sam is hiding something but decides to focus on a new murder case where they run into Cole. The three team up and learn a Khan worm is infecting men and turning them into murderers. Unfortunately, the worm makes its way into Cole.
Elenco: Jensen Ackles , Jared Padalecki , Misha Collins , Alexander Calvert , Mark Pellegrino , Mark Sheppard , Alona Tal , Candice Accola , Felicia Day , Genevieve Padalecki , Jeffrey Dean Morgan , Julie McNiven , Katie Cassidy , Lauren Cohan , Osric Chau , Richard Speight Jr. , Rob Benedict , Samantha Ferris , Ty Olsson .