This season saw the introduction of the Black and White Guardians as well as the companion Romana, who became only the second female Time Lord companion since Susan. This season is sometimes colloquially known as The Key to Time season after the story arc involving the Key to Time. Although not the first season to consist of linked stories (Season 8 in 1971 was the first, as all the stories that year featured the Master), it was the first to be recognised as having a series long arc. Although multi serial arcs would occur again, such a full- season experiment wouldn't be attempted again until Season 23. The arc has a number of similarities to the Season 1 story The Keys of Marinus. The storyline was originally proposed for Season 15, but it required more planning.

Season 16 Episode 21 - The Armageddon Factor (1)

Searching for the sixth segment, the Doctor and Romana land in the midst of a brutal nuclear war between the planets Atrios and Zeos. Air Date : 20th-Jan-1979

Season 16 Episode 1 - The Ribos Operation (1)

The Magellanic Clouds, the planet Ribos, an unknown time. Ordered by the White Guardian to collect the pieces of the omnipotent Key to Time, The Doctor, K-9 and his new assistant Romana arrive. Collecting the first segment is not going to be easy… Air Date : 2nd-Sep-1978  Read More

Season 16 Episode 2 - The Ribos Operation (2)

Trying to obtain the first segment of the Key to Time, the Doctor and Romana are swept up in an elaborate con. The target – the homicidal Graff Vynda K. Air Date : 9th-Sep-1978  Read More

Season 16 Episode 3 - The Ribos Operation (3)

Prisoners of the maniacal Graff Vynda K, the Doctor and Romana must break out and pursue the first segment – even as Unstoff takes it into the most dangerous place on Ribos. Air Date : 16th-Sep-1978  Read More

Season 16 Episode 4 - The Ribos Operation (4)

Trapped in the catacombs between a mad warlord and ravenous monsters, the Doctor and Romana work desperately to obtain the segment of the Key to Time - and escape alive. Air Date : 23rd-Sep-1978  Read More

Season 16 Episode 5 - The Pirate Planet (1)

Planet Zanak, unknown time. The Doctor and Romana are seeking the planet Calufrax where the second segment waits. They are in the right place and the right time… but on the wrong planet. Air Date : 30th-Sep-1978  Read More

Season 16 Episode 6 - The Pirate Planet (2)

The Doctor begins to investigate the mysteriously wealthy planet Zanak. Mentiads, a deranged Captain, strange omens, miraculous mines – what does it all mean? And what does it have to do with the Key to Time? Air Date : 7th-Oct-1978  Read More

Season 16 Episode 7 - The Pirate Planet (3)

The Mentiads take the Doctor, Romana and Kimus to a reunion with K9 and Mula, where they set about trying to defeat the Captain. Air Date : 14th-Oct-1978  Read More

Season 16 Episode 8 - The Pirate Planet (4)

The Captain and Xanxia work toward their secret goals. Both depends on the pirate planet consuming one more victim - Earth. Air Date : 21st-Oct-1978  Read More

Season 16 Episode 9 - The Stones of Blood (1)

England, the late 1970s. The Doctor and Romana arrive in search of the third segment. But the Tracer readings are erratic and something ominous is happening with an ancient stone circle... Air Date : 28th-Oct-1978  Read More

Season 16 Episode 10 - The Stones of Blood (2)

The quest for the Third Segment has landed the Doctor and Romana in the midst of a druidic cult centred on a stone circle. But the stones are not what they seem, and somewhere out there is a blood-thirsty Celtic goddess. Air Date : 4th-Nov-1978  Read More

Season 16 Episode 11 - The Stones of Blood (3)

Chased by blood-thirsty stones, the Doctor must find a way to rescue Romana. What awaits him in the theoretical absurdity of hyperspace? Air Date : 11th-Nov-1978  Read More

Season 16 Episode 12 - The Stones of Blood (4)

Facing a sentence of death from merciless justice machines, the Doctor must play for time while Romana tries to discover just who Vivian Fey really is. Air Date : 18th-Nov-1978  Read More

Season 16 Episode 13 - The Androids of Tara (1)

Arriving on Tara, Romana locates the fourth segment of the Key to Time with ease. But getting it away proves more difficult, as she is captured by the scheming Count Grendel who wants the throne of Tara for himself. Air Date : 25th-Nov-1978  Read More

Season 16 Episode 14 - The Androids of Tara (2)

The Doctor must employ a desperate gambit to keep the evil Grendel off the throne. And the Count has a new pawn to play - Romana. Air Date : 2nd-Dec-1978  Read More

Season 16 Episode 15 - The Androids of Tara (3)

The battle for control of Tara turns into a duel of wits between the Doctor and Grendel. But the Count shows he has more treacherous tricks up his sleeve. Air Date : 9th-Dec-1978  Read More

Season 16 Episode 16 - The Androids of Tara (4)

Grendel plans two weddings and a funeral to cement his hold over Tara. The Doctor and K-9 race to foil him and save the Time Lady's life. Air Date : 16th-Dec-1978  Read More

Season 16 Episode 17 - The Power of Kroll (1)

The Third Moon of Delta Magna, The Future. The Doctor and Romana arrive in search of the fifth segment and are immediately swept up in a conflict between the crew of a new refinery and the embittered natives… Air Date : 23rd-Dec-1978  Read More

Season 16 Episode 18 - The Power of Kroll (2)

The Doctor and Romana try to avoid being sacrificed to Kroll – just in time for the real monster to appear. Air Date : 30th-Dec-1978  Read More

Season 16 Episode 19 - The Power of Kroll (3)

The massive Kroll is awake and killing anyone in its path. And the swampies are determined to appease it – by sacrificing the Doctor and Romana. Air Date : 6th-Jan-1979  Read More

Season 16 Episode 20 - The Power of Kroll (4)

The Doctor and Romana are trapped between the monstrous Kroll and the insane refinery commander. And there is no sign of the fifth segment of the Key to Time. Air Date : 13th-Jan-1979  Read More

Season 16 Episode 21 - The Armageddon Factor (1)

Searching for the sixth segment, the Doctor and Romana land in the midst of a brutal nuclear war between the planets Atrios and Zeos. Air Date : 20th-Jan-1979  Read More

Season 16 Episode 22 - The Armageddon Factor (2)

Swept up in an apocalyptic war, the Doctor must help the Marshal defend his planet. But who or what controls the Marshal? Air Date : 27th-Jan-1979  Read More

Season 16 Episode 23 - The Armageddon Factor (3)

The Doctor meets a new enemy – the Shadow – who wants the Key to Time. And the Atrian-Zeon war is approaching an awful climax. Air Date : 3rd-Feb-1979  Read More

Season 16 Episode 24 - The Armageddon Factor (4)

The Doctor is forced into a desperate gambit to prevent a massacre. But it is getting harder to tell friend from foe. Air Date : 10th-Feb-1979  Read More

Season 16 Episode 25 - The Armageddon Factor (5)

The Doctor and Romana finally venture into the Shadow's lair. The Shadow appears to hold all the cards but the Doctor has found an old friend. Air Date : 17th-Feb-1979  Read More

Season 16 Episode 26 - The Armageddon Factor (6)

The Doctor and the Shadow have their final confrontation to take control of the Key to Time. Completing it may entail an awful sacrifice. And the Black Guardian will do anything to obtain it and plunge the Universe into chaos. Air Date : 24th-Feb-1979  Read More