Rory Williams and Amy Pond rendezvous with The Doctor and his Tardis in a large crop circle to hear as to whether The Doctor has found Melody Pond, the Ponds daughter. Mels, a friend of the companion turns up in a stolen vehicle and pulls out a gun on everyone and bundles them into the Tardis.
Mels is a close friend of the Williams, having been responsible for them getting together. We see a selection of scenes of the three of them throughout their time as youngster. We see Mels answering history questions blaming the Doctor as to why things happened such as the Titanic sinking.
Its 1936 and the nazi party is in control. A Teselecta disguised as a janitor makes his way into the office of a senior officer and miniturises him and teleport him into the Teselecta's body. The German is attacked by jelly like antibodies and is killed.
Back in the present, Mels shoots her gun in the Tardis causing it to malfunction and gas to be released. The Tardis lands in Germany just before the war and prevents Adolf Hitler from being shot by a fellow Nazi Member. When the Companions leave the Tardis, Mels is shot by Hitler. Rory punches Hitler and puts him in a cupboard. Hitler's bullet hits Mels who goes into regeneration mode and becomes River Song.
River Song tries to kill the Doctor but every plan was thwarted until the last one when river kisses the Doctor with poison on her lips. The Doctor orders Rory and Amy to go after River whilst he tries to find a cure for the poison. Outside, River has despatched a group of soldiers and stolen a bike. When the companions arrive, they are able to overpower a Nazi soldier and chase after River Song.
River has gone into a cabaret and ordered everyone to strip so she can get new clothing and with everyone running out of the building, the Companions have found where River is. Before Amy and Rory can run inside, they are miniaturised and teleported inside the Teselecta. Inside the Teselecta, they are to be killed by the antibodies but are saved at the last moment.
The Teselecta enters the cabaret and captures River Song and puts a stasis field round the body. The Doctor appears dressed for a night out in the thirties. The Doctor is still weak from the poison and can't do much.
Rory and Amy are inside the head of the Teselecta and they disable the security protection on theirs and every ones wrists that protect them from the antibodies. The crew of the Teselecta teleport out leaving Amy and Rory on their own against the antibodies. They are saved at the last minute when the Tardis appears to protect them, piloted by River Song.
The Tardis returns to where the Doctor is and everyone disembarks. Amy and Rory beg for help and River uses her remaining re-generations in order to save the Doctor. River Song wakes up in bed surrounding by everyone.