The Doctor (Peter Capaldi) and Clara (Jenna Coleman) are captured by Vikings and taken to a village. The Doctor claims to be Odin, but nobody believes him. The figure of Odin appears in the sky and offers to take the warriors to Valhalla. Warriors in armour appear and apparently disintegrate the villagers. Clara is a victim, as is a young woman named Ashildr (Maisie Williams).

The disintegrated find themselves on a spacecraft with other Vikings. The men are killed, and their bodies drained of adrenaline and testosterone. Clara and Ashildr meet Odin (David Schoefield), the leader of the merciless species The Mire. Before Clara can stop her, Ashildr declares war on them and Odin grants 24 hours to prepare. Back on Earth, Clara apprises the Doctor of the situation. Knowing that the villagers don’t have a chance in a fight, he puts together a plan using Ashildr’s storytelling skills and some electric eels. We’re not supposed to ask how electric eels got from South America to Viking territory in the 12th Century.

When the Mire arrive, they find the village celebrating. The Doctor stuns them with electricity and pulls off a warrior’s helmet with electromagnets. He alters the helmet and gives it to Ashildr to wear. He is able to project a dragon puppet to huge size, which scares off the Mire. The Doctor threatens to send video of their rout in terror throughout the universe, particularly embarrassing because Clara used an app to add the Benny Hill Theme.

Ashildr is found dead from the helmet’s effects. He modifies two chips from the helmet and implants one in Ashildr. She awakes, regenerated. The other chip he gives to her father to pass on to someone she cares for. As the Doctor and Clara leave in the TARDIS, he tells Clara that he may have given Asildr a terrible gift, since she is now virtually immortal.

This was the 100th episode since the 2005 revival of Doctor Who. The Doctor speaks baby. In modifying the helmets, he reverses the polarity of the neutron flow. He flashes back to The Fires of Pompeii, where the Doctor, played by David Tennant, met Caecillus, played by Peter Capaldi. He thinks he chose that face for regeneration to remind himself to save at least one person in every disaster. Odin’s appearance in the sky has a definite Monty Python air about it, particularly as he is played by David Schoefield, who played Zaphod Beeblebrox in Hitchhiker’s Guide to the Galaxy. Odin was supposed to be played by Brian Blessed, but he was ill. The story was well received, and Maisie Williams was highly praised. We know her as the Emmy-nominated Arya Stark in Game of Thrones, her first role. Her brother Robb Stark was played by Richard Madden, Jenna Coleman’s boyfriend.