With an episode name like "Let's Kill Hitler," you know something's gonna happen that'll mess with history. Sure enough, Moffat delivers. The Doctor and his friends pick up a stray passenger who holds our hero at gunpoint and decides to go to 1940s Nazi Germany. Why? "[The Doctor has] a time machine, [she's] got a gun. What the hell, let's kill Hitler." While killing Hitler is all well and good, and lots of people would love to do it, killing Hitler too early would skew history in some very unpredictable ways. Can the Doctor set things right? There are the people who punched Hitler and then there are the people who have killed him.