In an abortive attempt to repair the TARDIS and escape his exile, the Doctor makes a landing in the Australian outback. There he is captured and taken to Rudolph Steiner's hi-tech Gemini complex. Steiner intends to launch a missile at Venus which will propel it into Earth's orbit. However, Steiner's assistant, Stephens, has calculated that Steiner's plan will lead to the destruction of Earth. Together with a tribe of Aborigines, the Doctor and Stephens desperately try to prevent Steiner's missile from reaching its target.

Whilst walking on Dartmoor, the Doctor encounters a party of World War II German soldiers. Accidentally transported back in time to Nazi occupied France, the Doctor discovers that a Professor Vedrun is being forced by the Germans to develop a matter transporter. Inadvertenly, the Professor has constructed a device that can move people through time as well as space. With the help of Vedrun and the Doctor, the German commander, Spiegal, intends to journey through time to acquire advanced weaponry which will assure a Nazi victory in the war. When the Doctor and Vedrun are rescued from the chateau by the resistance, Spiegal threatens to destroy a school full of children if the escapees are not returned. With Spiegal's deadline approaching, the Doctor must devise a way to save the children and prevent Spiegal from diverting the course of history.

Having successfully repaired the TARDIS, the Doctor journeys into space and lands on a starship manned only by robots and carrying a cargo of unconscious people. Awakening a girl called Trandi, the Doctor discovers that her people, the Crallicans, have been enticed away from their dying world by the evil Vogans. Taking Trandi in the TARDIS to the starship's destination, the Doctor discovers that the Vogans intend to use the Crallicans as slave labour to mine the Voganite minerals which they depend on. In a pretence of cooperation, the Doctor agrees to shuttle the slave from the ship to the planet's surface in the TARDIS. However, as soon as the operation is complete, the Vogans intend to destroy the Doctor and the TARDIS with a bomb.

On the Minister of Defence's orders, the Doctor is abducted from his holiday cottage and taken to the village of Puddlesfield. There he is shown the cast and crew of a Bbc drama who have all been turned into plastic. Investigating on his own, the Doctor discovers that most of the villagers have become the plasticised slaves of evil genius, Professor Midas. The Professor intends to use his plastic ray weapon to control the world but first he must rid himself of the only person who stands in his way - the Doctor.

In the London of 1863, the Doctor becomes the victim of a young pick-pocket, Charlie Fisher. However, both end up in the dock when the Doctor absentmindly tries to give a cabby a Seventies' bank-note. With Charlie's help, the Doctor escapes with his young companion to the TARDIS. Intending to give Charlie a new start, the Doctor pilots the TARDIS to America where the two become embroiled in the battle of Gettysburg. After meeting President Lincoln and ensuring a victory for the North, the Doctor and his companion discover that the TARDIS has been confiscated by General Grant. To retrieve it, the Doctor and Charlie become the reluctant partners of two southern outlaws.

The Doctor and the TARDIS are abducted by Andron, a member of the time police from the far-flung future of England. Imprisoned in a stasis box with Victorian time-traveller Theophillus Tolliver, the Doctor learns that they are in New Britain which is governed by someone or something called Mar-Kom who has outlawed time travel. Subjected to trial-by-combat with a robot, the Doctor and Theo discovers that Mar-Kom is in fact a giant robot controlled by a vast computer installed in St Paul's Cathedral. With the population of Earth frozen in time, the Doctor and Theo fight to overpower the mad computer's rule before its robotic forces can stop them.

The Doctor discovers that his old adversaries, the Daleks, have amassed a secret armada of ships over the last three centuries. The Daleks intend to take over the world by turning humans into Daleks. Their first step is to launch a nuclear on Sydney in Australia. The Doctor realises that attacking the Daleks by conventional means would be futile. Instead, he and his naval friend infiltrate the Dalek stronghold in Sydney harbour in the hope of defeating the Daleks from the inside.

A burglar, Finney, attempts to steal the TARDIS. Accidentally causing a fire, the Doctor use the Ship to escape with Finney. The TARDIS is drawn to the Dalek's home planet by their time vector machine where the Doctor is apparently transformed into a humanoid Dalek. However, the Doctor is in fact unharmed and attempts to destroy the Daleks by piloting the TARDIS into a star. When the attempt fails, the Doctor and Finney escape into the wilderness of the Dalek's home world but find themselves trapped between the creatures and a giant prehistoric beast.

After colliding with an exploding galaxy, the TARDIS takes the Doctor to England in the year 5000. There, in the ruins of the British Library, the Doctor meets the last remaining men, or 'norms', on Earth. The TARDIS is carried off by a giant airship piloted by a race of mute supermen known as the 'mutants'. Defeating the leader of the mutants the Doctor saves the TARDIS from destruction. With the norm, Brod, the Doctor travels to New York in 1872. There they seek out Professor Cassells whose biological experiments were the original cause of the Earth's devastation in the future. However, unable to believe the Doctor's incredible story, the Professor refuses to halt his research.

The Doctor is invited to Dowmphilly tracking station to observe the launch of a new space platform. However, the platform is in fact a launch pad for a nuclear arsenal. When a mysterious object is detected approaching earth it is assumed to be a meteor and, despite the Doctor's warnings, the space platform use it as target practice for a nuclear missile. As the missile has no effect it soon becomes clear that the object is a spacecraft, In retaliation, the space platform is apparently destroyed. Fearful that the Earth has instigated a space war what it cannot hope to win, the Doctor travels in the TARDIS to the alien vessel to confront its unseen occupants.

The TARDIS is forced to land on an alien world infested by plants and fungi. The Ugrakks have learnt of the Doctor and his TARDIS from an Earth space traveller, Professor Lammers. Under constant attack from the giant Zama flies, the Ugrakks are desperate to escape their world to find a new planet. Unable to travel in space by conventional means, the Ugrakks are eager to make use of the Doctor and his TARDIS which will be able to transport them without ill effect. Unwilling to submit to the demands of the Ugrakks, the Doctor takes advantage of a Zama fly attack and escapes with Professor Lammers. When the Doctor discovers the Zama fly grubs beneath the organic city of the Ugrakks, he hatches a plan that will put an end to the evil plant creatures once and for all.

The Doctor witnesses the kidnapping of nuclear physicist Simon Trent and his young son. Giving chase, the Doctor is himself captured and taken to an island belonging to the apparently alien General Steelfist. Both Trent and later the Doctor are transported to a space station orbiting the Earth. There they are forced to construct a nuclear device with which Steelfist intends to blackmail the world. However the Doctor becomes suspicious of the mysterious Steelfist and discovers that the space station is in fact the top of a lighthouse close to the island. With the help of old beachcomber, Arnie Babbs, the Doctor and Trent escape. But is Babbs the friend that he appears to be?

The Doctor shelters from an attack on his mind in the TARDIS where he identifies the source as being an alien spacecraft on the fringes of the solar system. Travelling to London, the Doctor intends to warn the Minister of Defence about the imminent invasion. However, the Doctor discovers the minds of the entire population of Earth have been neutralised by the approaching Zeron invaders. Teaming up with an unaffected American tourist called Nick, the Doctor uses the resources of the Post Office tower to counteract the Zeron mind control. Fearful of looking foolish if the Doctor should be wrong, the British Government refuse to alert the world to the threat of the Zeron invasion. With the help of Nick's disc jockey cousin Jed, the Doctor broadcasts his own warning over the radio. As the Zerons once again bombard the Earth with their mind-control ray, the Doctor leads his friends to the safe depths of the London Underground. However, the Zerons are aware of the Doctor's refuge and take steps to neutralise the threat he poses towards their conquest of Earth.

The Doctor joins a group of top scientists at one of several conferences that are simultaneously taking place around the world. The project has been masterminded by the Abbot of Mai'Sung who incapacitates all of the attendees with nerve gas. The Doctor makes a swift recovery and accompanies his still comatose colleagues when they are delivered in to the hands of the Abbot who has the only cure to the effects of the gas. The Abbot intends to combine his own knowledge of the ancient mysteries with the scientific wisdom of the Doctor and his colleagues to run the world.

While on a fishing holiday in Scotland, the Doctor encounters a group of archaeologists who are investigating the legend of the Glen of Sleeping. One of the scientists is in fact the Master in disguise who summons Red Angus his clansmen from their centuries-long sleep. With Angus and his men under his command, the Master intends to use them to capture a nuclear submarine in a near loch. The Doctor traces the cause of the clansme's long slumber to two chronons, an alien time-trap device. Using the chronons the Doctor is able to send himself, the Master, the submarine and the clansmen back to 1745. Pursued by Red Coats, the Doctor may never be able to escape back to the twentieth century.

Neutralising Earth's satellite network, the Daleks are able to land a flying saucer beneath the sea and establish a control area. The Doctor suspects an invasion but Whitehall refuse to take his recommendations seriously. Using the TARDIS to investigate, the Doctor infiltrates the Dalek craft just in time to witness the Daleks' subjugation of a Royal Navy nuclear submarine by mind control. The Doctor is able to turn the Daleks' plan to his advantage when he orders the submarine commander to fire upon the Dalek craft. However, the Doctor may not be able to escape to the TARDIS before the missile strikes.

At the request of the Ministry, the Doctor investigates a new solar power station in Wales called Station 40. The station's director, Sir Nigel Lomax, refuses to acknowledge the potential danger of the project and appears to be working to his own agenda. The Doctor discovers that some years ago, Lomax apparently escaped death in a volcano by making contact with an alien life-form that requires intense heat to survive. Attempting to recreate a new habitat for his alien masters, Sir Nigel intends to put a permanent end to the Doctor's interfering.

In a bid to replace the failing Marlenial elements of the TARDIS, the Doctor journeys to a planet threatened by the imminent destruction of its star. Captured by a giant gorilla-like monster, the Doctor is imprisoned in an underground complex. There he is forced to participate in many tests of skill and endurance, all of which could result in his death.

At the bidding of the Time Lords, the Doctor travels to the polluted planet of Farraf. There he discovers that the evil warmonger, Lord Soton, intends to use the TARDIS to invade the idyllic neighbouring planet Raffar. Escaping from his prison cell, the Doctor attempts to warn the pacifistic Rafs of Soton's threat.

The Doctor and his young friend, Tom, are sucked into a strange tornado in space. Regaining consciousness they find themselves aboard a giant biological computer that is collecting specimens of different life-forms as it travels through space. Passing several intelligence tests and duping their captor, the Doctor and Tom attempt to return Earth by reversing the vessel's programming.

Returning to Earth in the TARDIS, the Doctor is effected by the testing of a new military satellite that uses sound waves to destroy its target. Although the test his successful, the satellite's transmissions cannot be terminated and to avoid widespread devastation it is retuned to a higher frequency. Unfortunately, although the high frequency sound-waves are inaudible to humans they are heard by the Earth's animals who are driven wild by the noise. The Doctor lands the TARDIS at the satellite's control centre on a Scottish island. There he attempt to convince the base commander to destroy the satellite before the animals destroy the world.

A giant, malevolent monster lands in Portsmouth harbour and attacks a naval vessel. Assisted by Captain Fenton, the Doctor defeats the cosmic creature by using vast quantities of paint to disrupt its force field.

The Doctor attends the performance of master magician, Chang. The Doctor realises that Chang is an alien who is using his act as a cover to abduct humans for experimentation on his home planet. Chang is electrocuted when he attempts to escape the Doctor.

Wile inspecting UNIT, a pompous civil servant, Sir Norman Ormsby, steals the Doctor’s new Time-Shrinker drug. When the greedy Ormsby takes the drug and heads to London at the speed of sound he rapidly ages and is incinerated by air friction.

Using alien mist flowers from the planet Sarkan, the Master lures the Doctor to the seaside resort of Tadcaster by enshrouding the town in a dense fog. The Master relishes in his opportunity to taunt the Doctor who is effectively blinded by the fog. However, the Master has reckoned without the interference of the Doctor's blind companion Joe, who does not need to rely on his eyes. The Doctor and Joe pursue the Master to his pier-head hideaway. Desperate to stop him from making the Sarkan mist flowers bloom, the Doctor and Joe take drastic action.

The Doctor and the Brigadier pursue master galactic criminal, Hingrad through the London Underground. The Doctor discovers Hingrad's layer in the Tower of London. Intent on stealing the crown jewels, Hingrad leaves the Doctor imprisoned in stocks to be killed by an ancient cannon.

The Brigadier alerts the Doctor that someone has set Whitepoint nuclear power station to explode. At Whitepoint, the Doctor and Sarah discover that the alert has been a hoax set up to test UNIT’s efficiency.

In the TARDIS, the Doctor and Sarah Jane observe the premature formation of a galactic cyclone. The Doctor discovers that the cyclone will pass close to Earth, smothering it in a poison gas cloud. Back on Earth, the Doctor imparts the terrible news and the Brigadier oversees emergency to ensure the survival of the chosen few. However, the Doctor suspects alien involvement and discovers the Zirconian fleet have instigated the cloud. Using a radio telescope and Earth's satellites, the Doctor plans to deflect the deadly cloud away from Earth.

Despairing of the twentieth century and its traffic congestion, the Doctor takes Sarah Jane on a holiday to nineteenth century Paris. However, the TARDIS materialises in Paris, Texas, instead of France. The travellers join a wagon train which is besieged by Indians. The cowboys stage a diversion and the Doctor and Sarah Jane return to the TARDIS and encounter the Indian chief, War Eagle. The Doctor overpowers War Eagle and the TARDIS travels to Paris, France, where War Eagle escapes. Worried that they have let loose a murderous savage in civilised Paris, the Doctor and Sarah Jane give pursuit.

At his cottage, the Doctor is running repairs on the TARDIS. Distracted by Sarah Jane, the Doctor causes the TARDIS to jump sideways in time to a parallel Earth. There they are captured by two dangerous criminals identical in appearance to themselves. In a bid to escape from the two villains, the Doctor attempt to push the TARDIS into yet another parallel world.

The Doctor and a young boy, Dave Lester, journey to the mysterious Carradine estate. There they find deranged genius Professor Rayner has created a huge Master Plant which can harness and control all other plants. The Professor's plans for world domination are thwarted when the Master Plant kills him. Besieged inside the Professor's laboratory by an approaching army of plants, the Doctor has only minutes to concoct a way of defeating the apparently unstoppable Master Plant.

When Sir Henry Felton disappears from his chauffeur driven car whilst in transit, the Doctor suspects alien interference. Repeating Felton's journey, the Doctor is also spirited away by a matter transmitter hidden in Sir Henry's Rolls-Royce. Sir Henry and the Doctor discover that those responsible are advanced aliens from the Crab Galaxy. Aware of Sir Henry's development of a matter transmitter, the aliens are fearful that mankind will use the discovery to spread their war-like ways across the universe. As the security forces come to the rescue of the Doctor and Sir Henry, the aliens escapes by the matter transmitter. Sir Henry is left to decide if the world is ready for his discovery.

The Doctor jumps ship when the TARDIS is drawn into a living planet. On the planet, the Doctor meets a fellow castaway, Harry Trant. The Two hitch a ride inside a giant parasite which takes them to the planet's stomach and the TARDIS. To escape the creature, the Doctor and Harry must first kill it.