The Doctor and her companions are reunited under grave circumstances when an unknown species of interdimensional aliens attacks intelligence agents around the world. With Yas and Ryan dispatched to investigate a tech mogul, the Doctor introduces Graham to an old acquaintance from MI6.

An effort to escape the enemy's trap leaves the Doctor in the nineteenth century, skipping through time with the Master on her heels. Meanwhile the others are sent on the run with no way to prevent Barton's plan, and the Kasavin's interdimensional invasion.

The Doctor and her companions' holiday at Tranquility Spa comes to a quick end after the high-tech facility comes under attack by a predator who has infiltrated the facility.

In the early twentieth century the famous inventor Nikola Tesla discovers a piece of alien technology, making him the target of an alien species -- and pulling the Doctor and her companions into his feud with Thomas Edison.

The Judoon erect a security perimeter around Earth while they hunt for a fugitive -- leading the Doctor to a seemingly ordinary couple who harbor an unimaginable secret. Meanwhile, the Doctor's companions have a close encounter with one of her old friends.

The arrival of a deadly plague on Earth sends the Doctor and her companions on an investigation all across the globe, where they are drawn into an alien search for the cure.

While the Doctor's companions enjoy some R&R back home, the Doctor finds a young woman in fourteenth-century Syria -- apparently the only survivor of a creature that has attacked an ancient hospital. But a very different sort of evil is about to make all of them feel his presence.

The Doctor and her companions visit Lord Byron and Mary Shelley to hear a good ghost story in the middle of a thunderstorm in 1816, but find that the house where they are staying is full of haunted secrets.

In the distant future the Doctor fails in an attempt to defend a group of human refugees from the Cybermen, leaving her separated from some of her companions -- which a vengeful Cyberman chases them across the galaxy.

The Master takes the Doctor to the ashes of Gallifrey, where he plans to reveal a shocking personal truth about her past -- while the army of the Cybermen also approach the planet, with the hope of dominating the galaxy.