Ep 8. Let's Kill Hitler

In Doctor Who (2005) season 6 episode 8, titled "Let's Kill Hitler," the TARDIS is hijacked by the Doctor's old school friend, Mels, who turns out to be a regenerated version of his enemy, the Master. Mels, in her new form, shoots the Doctor and they crash land in Berlin, 1938, on the eve of World War II.

The Doctor's companions, Amy and Rory, follow them to Berlin and discover that Mels has taken on the persona of a Nazi officer and plans to assassinate Adolf Hitler. The Doctor, still recovering from his gunshot wound, insists that they focus on finding out how Mels became the Master and stop her from causing any more chaos.

As they try to track down Mels, they cross paths with a group of Nazi officers, who capture them and take them to see Hitler himself. The Doctor convinces Hitler and his officers to let them go, but not before discovering that Mels has been fatally poisoned.

In a race against time, the Doctor uses the last of his regenerative energy to revive Mels and transform her into a new incarnation of River Song, who he recognizes as his future wife. Together, they discover the real threat lurking in Berlin: a group of shape-shifting robots called the Teselecta who are out to execute a war criminal.

In an action-packed chase scene, River and the Doctor team up to stop the Teselecta and save their target, proving that sometimes the biggest threat is not what it seems. As the TARDIS takes off, Amy and Rory ponder the unfolding mystery of their friend, River Song, and the Doctor's enigmatic past.

Overall, "Let's Kill Hitler" is a thrilling and fast-paced episode that plays with time and politics in typical Doctor Who fashion. It introduces a new character, River Song, while also hinting at the deeper mythology of the show. It's a must-watch for any fan of the series.