Trying to get to a concert in Sheffield in 1979, the Doctor (David Tennant) and Rose (Billie Piper) accidentally land the TARDIS in 1879. The Royal Train has been blocked by a fallen tree on the line to Aberdeen and Queen Victoria (Pauline Collins) has been forced to travel by carriage to Balmoral Castle. Using his psychic paper, the Doctor poses as the Queen’s Protector and the time travellers ride across the Moors to Torchwood Estate, a favourite of the late Prince Albert.

The estate has been seized by a group of monks following Father Angelo (Ian Hanmore) and they have forced the owner, Sir Robert MacLeish (Derek Riddell) to play along. They have cut down the tree along the rail-line to get the Queen to this place and pretend to be the servants and guards of the house. They have brought a man they call the Host (Tom Smith), infected with a lycanthropy virus, hoping to turn Victoria into the Queen of the Werewolves.

The Doctor helps to save Rose, the Queen, and Sir Robert by locking them in the library, treating the wood with oil of mistletoe, which repels werewolves. Who knew? In the library collection is evidence collected by Sir Robert’s father and by Prince Albert, showing that werewolves are actually the current form of an alien species. The Doctor understands that the estate is a werewolf trap. Using an unusual telescope and the Koh-i-Noor diamond, cut by Prince Albert, it is possible to destroy the alien lifeform.

Sir Robert sacrifices himself to allow the others to prepare the telescope in the observatory. They trap the werewolf in the concentrated light of the full moon. The next day, the Doctor and Rose are knighted and then banished from the British Empire. In honour of Sir Robert, the Queen orders the creation of the Torchwood Institute to defend Britain from alien attacks. But the Doctor, as an alien she doesn’t trust, is banned.

In the beginning, the Doctor introduces himself as James McCrimmon, who was a companion of the Second Doctor. David Tennant uses his family’s accent in the episode, and in fact his parents were allowed to read out the script in rehearsal. Martial arts films like Crouching Tiger, Hidden Dragon were studied for the opening fight sequence. At one point, Billie Piper’s hair caught fire. The werewolf was CGI. Pauline Collins, who played Victoria, had been offered the role of companion in 1967, but turned it down.

The Doctor is posing as a Scottish physician and claims to have studied under Doctor Joseph Bell at the University of Edinburgh. Bell was a mentor of Sir Arthur Conan Doyle and the model for Sherlock Holmes. At first, Rose was supposed to fake a Scottish accent, but Billie Piper’s accent was awful. The young man who becomes a werewolf is called the Host or the Lupine Wavelength Haemovariform. He was played by Tom Smith, who went to Drama School with David Tennant. Mistletoe is not indigenous to Scotland, so it would have to be imported to repel werewolves. When the wolf sees Rose, he picks up on the Bad Wolf in her.