In the prequel, Amy (Karen Gillan) calls the Doctor (Matt Smith) and leaves a message on the phone, begging him to help her find her child, Melody. Though Amy knows Melody will grow up to be River Song (Alex Kingston), she does not want to miss her growing up. The Doctor is listening but does not pick up.

In modern-day Leadworth. Amy and Rory (Arthur Darvill) create a crop circle to get the Doctor’s attention. He arrives in the TARDIS, but Amy and Rory’s childhood friend Mels (Nina Toussaint-White) gets them to travel back in Time to kill Hitler. Inside the TARDIS, Mels fires off a gun, sending the TARDIS out of control.

In 1938 Berlin, a shape-changing, human-looking robot called a Teselecta, with a future human crew miniaturized inside it, is out to visit justice upon Hitler (Alment Welling). The TARDIS crashes into Hitler’s office and knocks over the Teselecta. Hitler shoots at it but hits Mels instead. Rory locks Hitler in the cupboard. Mels regenerates into River Song, because the Ponds’ childhood friend Mels was really their long-lost daughter Melody Pond. As River was trained by her captors to kill the Doctor, she kisses him with poisoned lipstick. The Doctor will die within the hour. He orders Amy and Rory to follow River, while he returns to the TARDIS. The Teselecta, knowing that the Doctor’s death is a fixed point in time, follows River. As a fugitive who is responsible for the Doctor’s death, she is on their wanted list.

The dying Doctor stops the Teselecta from punishing River at the Hotel Adlon. The Captain, Carter (Richard Dillane), tells the Doctor that River was trained by the Silence, a religious order that believes silence will fall when the oldest question in the universe is asked. Amy forces the crew to abandon the Teselecta. Amy, Rory, and River find the Doctor near death. He whispers a message for River in River’s ear. But River is still Melody and asks Amy who River is.

Amy shows her the Teselecta’s records. River sacrifices her remaining regenerations to bring the Doctor back to life, then passes out. They take her to a hospital in the far future, leaving a diary as a gift by her bedside, and then they leave in the TARDIS. From the Teselecta records, the Doctor now knows when he will die.

The fast-paced, lighthearted episode received excellent reviews. Alex Kingston pretty much stole every scene she was in. The Teselecta corridors were based on the Large Hadron Collider in Switzerland. The Doctor wears his green, double-breasted moleskin coat with gold buttons. There is a strange homage to the most famous scene in The Graduate. The crew of the Teselecta seem very much like a Star Trek crew. Hitler’s office is an extremely accurate reproduction of the original.