Supernatural Season 8 Episode 20

Concerned about the physical toll the second trial took on Sam, Dean benches his brother from hunting until he heals up. So, when geektastic hacker Charlie (guest star Felicia Day) stumbles upon a case and finds the boys, Dean decides it's time to teach Charlie how to be a hunter-in-training. While happy to see "her highness", the boys suspect Charlie is hiding something; a secret that could get her killed.