The series is the first to star Peter Capaldi as the Twelfth Doctor and Jenna Coleman as his companion, Clara Oswald. Also playing a major recurring role in the series is Samuel Anderson as Danny Pink, Clara's boyfriend. The main story arc revolves around a mysterious woman called Missy (portrayed by Michelle Gomez), who is often seen welcoming people who have died throughout the series to the "Promised Land", a place that serves as an apparent afterlife to deceased characters.

This is the first series to feature David Tennant as the tenth Doctor. He continues to travel with his companion Rose Tyler (Billie Piper), with whom he has grown increasingly attached. They also briefly travel with Rose's boyfriend Mickey Smith (Noel Clarke), and Camille Coduri reprises her role as Rose's mother Jackie. The series is connected by a loose story arc consisting of the recurring word "Torchwood". This is also the first series to be preceded by a Christmas special, which was commissioned to see how well the show could do at Christmas. The success of "The Christmas Invasion" led to the Christmas special becoming an annual tradition.

When the hospital she works at is transported to the moon, medical student Martha Jones joins forces with The Doctor to hunt down an alien fugitive before the oxygen runs out