Season 16

(4 episodes)

Having left Leela on Gallifrey, the Doctor and K9 Mark II don't remain footloose for long. The TARDIS is soon intercepted by the White Guardian, who assigns the Doctor an urgent mission to locate the six segments of the Key to Time, which are well disguised and hidden in odd corners of time and space. Once assembled, the Key will allow the White Guardian to restore balance to a universe descending into evil and chaos. To assist the Doctor, the White Guardian has appointed Romana, fresh out of the Time Lord Academy and none too well traveled. Despite an initial bout of "negative empathy," the Doctor and Romana trace the first segment's signal to Ribos, a remote, primitive planet that suffers from 32-year winters. There they are surprised to meet other interplanetary travelers, including two conmen, Garron and Unstoffe, and the Graff Vynda-K, a warlord who's in the market for an inexpensive planet to buy as a base.

Written by Robert Holmes

(4 episodes)

The Doctor and Romana arrive on the planet Zanak, looking for the second segment of the Key to Time. Although priceless gems are scattered on the streets, and the night sky changes with the dawn of each new prosperous age, the townsfolk live in fear. For in a fortress overlooking the city, the terrifying Pirate Captain is in control of the most destructive force in the galaxy.

Written by Douglas Adams

(4 episodes)

The search for the third segment of the Key to Time leads the Doctor, Romana and K-9 to Boscombe Moor on Earth in the late 20th century. Here they encounter Professor Amelia Rumford and Vivien Fay, who are surveying an ancient stone circle called the Nine Travellers. What is the link between an ancient Celtic goddess, an alien criminal and a transporter ship concealed in hyperspace? And can the Doctor escape the Druidic sacrifice of blood to uncover the mystery of the moving stones?

Written by David Fisher

(4 episodes)

It seems that the search for the fourth segment to the Key to Time will prove simple when Romana locates it on the planet Tara. But in a land where nothing is at it first appears, the Doctor and his companion quickly find themselves embroiled in a deadly game of kidnap, deceit and counterplot. It is not long before the Doctor finds himself locking swords with the dastardly Count Grendel of Gracht, the finest bladesman in the kingdom, who has sinister plans for Romana.

Written by David Fisher

(4 episodes)

Searching for the fifth segment of the Key to Time, the tracer leads the TARDIS to treacherous swamps on the third moon of the planet Delta Magna. The Doctor and Romana soon uncover a plot to wipe out the Swampies, the local inhabitants, by the duplicitous crew of a gas refinery. Meanwhile, a massive creature is stirring beneath the waters, and the primitive Swampies believe the only way to calm the powerful monster is human sacrifice.

Written by Robert Holmes

(6 episodes)

The Key to Time is almost complete. With only one piece still to find, the Doctor, Romana and K-9 arrive on Atrios, a planet in the middle of a terrible war with its twin world, Zeos. To restore the balance of the universe for the White Guardian, the Doctor must find the sixth segment before the planets destroy each other, but Zeos is deserted, so who is behind the war?

Written by Bob Baker and Dave Martin