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.

在一个行走、交谈、数字连接的机器人已经成为孩子们最好的朋友的世界里，《罗恩出事了》讲述了一个11岁的男孩发现他的机器人伙伴不太工作的故事。

电影《沙丘》为观众呈现了一段神秘而感人至深的英雄之旅。天赋异禀的少年保罗·厄崔迪（提莫西·查拉梅 饰）被命运指引，为了保卫自己的家族和人民，决心前往浩瀚宇宙间最危险的星球，开启一场惊心动魄的冒险。与此同时，各路势力为了抢夺这颗星球上一种能够释放人类最大潜力的珍贵资源而纷纷加入战场。最终，唯有那些能够战胜内心恐惧的人才能生存下去。

This season introduced K9 to the series and saw the departure of Leela. It was originally intended to include Terrance Dicks' story The Vampire Mutations but, due to a major BBC production of Dracula, it was postponed. It later became Season 18's State of Decay. To replace it, Dicks quickly scripted the season opener, Horror of Fang Rock. The season took a two week transmission break over the 1977 Christmas period, between the broadcast of part four of The Sun Makers and part one of Underworld.

银行出纳员盖（瑞安·雷诺兹 饰）发现自己其实是开放世界电子游戏中的背景角色，于是决定成为英雄，并改写自己的故事。现在，在一个没有限制的世界里，他决心以自己的方式拯救他的世界，以免为时过晚。

维基：

The Doctor and Sarah arrive in a quarry during blasting operations and when Sarah is buried under rubble, she discovers a stone hand.

维基：

S13E21-26
Two alien seed pods are found buried in the Antarctic permafrost and the Doctor realises that they are from a Krynoid, a form of plant life that infects and transforms all animal life on planets upon which it becomes established.
One of the pods infects a scientist at an Antarctic base but the developing Krynoid is destroyed by a bomb set by two men, Scorby and Keeler, who have made off with the other pod for their boss, eccentric plant collector Harrison Chase.
At his mansion in England Chase arranges for the pod to be opened under controlled conditions while a human host - Sarah - is held nearby. The Doctor rescues Sarah, but Keeler is infected. Keeler's transformation into a Krynoid is accelerated by Chase, who has him fed with raw meat.
The creature escapes and goes on the rampage, rapidly growing to giant proportions. Chase decides to turn the Doctor into compost by feeding him into a pulverising machine. The Time Lord escapes, but Chase falls into the machine and is killed. UNIT have meanwhile been called in, and they arrange for the Krynoid to be bombed before it can spread its pods across the Earth.

Philip Hinchcliffe era
The planet Karn is home both to a mystic Sisterhood, whose sacred flame produces an elixir of life, and to Mehendri Solon, a fanatical scientist who is using the remnants of spaceship crash victims to put together a new body for the still-living brain of the executed Time Lord criminal Morbius.
When the Doctor and Sarah arrive on the planet, Solon decides that the Doctor's head is just what he needs to complete his work. The Sisterhood meanwhile fear that the Doctor has been sent by the Time Lords to steal the last drops of elixir produced by the dying flame. They kidnap him and plan to burn him at the stake but he is rescued by Sarah, who is temporarily blinded in the process.
The Doctor is tricked by Solon into believing that his companion's condition is permanent. He asks the Sisterhood for help and restores their sacred flame to its former glory using a firework to clear its blocked chimney. Returning to Solon's citadel, the Doctor and Sarah become trapped in the cellar.
The Doctor releases cyanide fumes into the ventilation system and Solon is killed, but not before he has used an artificial brain case to complete Morbius's new body. The now-mobile Morbius accepts the Doctor's challenge to a mind-bending contest, which takes a heavy toll on both of them. The Sisters force the crazed Morbius over a cliff and he falls to his death. They then use the elixir to heal the Doctor.

The Doctor and Sarah reach Earth and try to warn the research centre about the Kraal invasion before Styggron unleashes his virus.

The TARDIS materialises on Earth in the year 1911 inside an old priory owned by Egyptologist Marcus Scarman. Scarman has been possessed by Sutekh, last survivor of the god-like Osirans, who is held prisoner inside a pyramid in Egypt by a signal transmitted from one on Mars. Sutekh desires his freedom and instructs Scarman to construct servicer robots - which look like Egyptian mummies - to build a missile with which to destroy the Martian pyramid. The Doctor foils this plan by blowing up the missile.
He then falls under Sutekh's control himself and is made to transport Scarman to Mars in the TARDIS. Scarman cuts off the signal but the Doctor, now freed of Sutekh's influence, realises that there will be a short delay before it ceases to have effect, owing to the time taken for it to reach Earth.
He rushes back and uses the time control from the TARDIS to move the end of the space-time tunnel that links the priory to the Egyptian pyramid into the far future. Sutekh, travelling down the tunnel, is unable to reach the end in his lifetime, and dies.

It was during this season that the Doctor cut ties to UNIT (after Terror of the Zygons, the Brigadier would not appear again until Mawdryn Undead in 1983, and The Seeds of Doom marked the last occasion to date that the Doctor was explicitly said to be working for UNIT - as opposed to working with them as occasions warranted). Several of the serials in this season, particularly Pyramids of Mars and The Brain of Morbius, are among the best-known of the 1970s-era storylines. Though it was aired as a part of Season 13, Terror of the Zygons was actually filmed as part of the previous season; this holdover allowed the series to switch back to an autumn season start.