Ep 11. Mawdryn Undead (3)

The Doctor, along with his companion Tegan and her cousin Nyssa, continue their search for the missing components to the TARDIS in the third part of the Mawdryn Undead story arc. They arrive at a remote corner of England in the year 1983, where they encounter a group of schoolboys who are connected to the tangled web of events surrounding the stolen TARDIS components.

Meanwhile, aboard an alien ship in orbit around Earth, the renegade Time Lord known as The Black Guardian is still trying to coerce the other Time Lord, Turlough, into assassinating the Doctor in exchange for his freedom. Turlough is torn between his loyalty to the Doctor and his desire to be free of the Guardian's influence, leading to a climactic confrontation between the two.

The Doctor and his companions encounter an old acquaintance of the Doctor's, Brigadier Lethbridge-Stewart, who is now retired and living in a house near the school where the boys are attending. Lethbridge-Stewart fills the Doctor in on the situation with the boys, who are somehow connected to a strange energy field that has been affecting him and the other members of a UNIT reunion party.

As the Doctor investigates the energy field, he discovers that it is being generated by a pair of aliens called the Mawdryn, who are attempting to gain access to the Time Lord's ability to regenerate in order to defeat their own genetic, immortal curse. The Mawdryn mistakenly believe that the Doctor can help them break this curse, but in reality, it is Turlough who holds the key to their salvation.

As the Doctor races to stop the Mawdryn from triggering a catastrophic explosion, Turlough is forced to confront the truth about his past and make a difficult decision about his future. The Black Guardian continues to manipulate events from the shadows, still hoping to turn Turlough against the Doctor, but even he can't predict the repercussions of the decisions made in this episode.

Mawdryn Undead (3) is a complex and gripping episode that builds on the storylines and character relationships established in the previous two episodes. Despite the high stakes and tense action scenes, there are still moments of humor and charm, particularly in the scenes with Brigadier Lethbridge-Stewart. This episode is a standout in an already memorable season of Doctor Who.