A mysterious explosion has knocked the TARDIS into void. And in their confusion, the crew are turning on one another.

Ian and Barbara believe the TARDIS has finally returned to their contemporary London, but soon discover signs of plague and warfare. Their old enemies, the Daleks, have invaded the Earth of the 22nd century. Separated and fighting for their lives, the travellers must try to aid the remaining humans and overthrow the Daleks' cruel tyranny. (Originally broadcast in six parts.)

The Doctor and Ian are taken to the Dalek saucer while Susan and Barbara join the rebels in planning an attack.

The Doctor manages to escape from the Dalek saucer and meet up with Susan and David but Ian is left trapped onboard. Meanwhile, Barbara and her new friends face a dangerous journey across London.

While Susan and David try to find a way out of London, Ian and Larry infiltrate the Dalek mine workings.

The Doctor's party investigate the Daleks' central control in Bedfordshire while Barbara and Jenny's attempt to reach it are derailed when they are betrayed.

The Daleks' plan to transform Earth into a giant spaceship and wipe out its inhabitants is nearing completion and the Doctor and his friends face a race against time to prevent them from destroying the planet's core.

The TARDIS is drawn by a mysterious force and lands on the alien planet Vortis. There the Doctor, Ian, Barbara and Vicki find themselves caught up in a war between an evil force known as "The Animus", its ant-like Zarbi allies, and the butterfly-like Menoptra race and their allies the subterranean Optera.

The Doctor, Ian and Vicki are captured by the Zarbi while Barbara meets up with the butterfly-like Menoptera who are trying to reclaim the planet.

The Doctor is forced to co-operate with the Animus but Ian uses the opportunity to make an escape attempt.

Ian and Vrestin are captured by the subterranean Optera while Barbara and her Menoptera allies attempt to escape from the slave camp.

Barbara and the surviving Menoptera take refuge in the Temple of Light while the Doctor and Vicki attempt to escape by taking control of a Zarbi.

The Doctor and Vicki are taken before the Animus but the isoptope is left behind in the laboratory.The only hope of victory lies with Barbara and her Menoptera allies.

The Daleks pursue The Doctor through time and space, with the intentions of exterminating him. Places they land include the Mary Celeste, a haunted house and the empire state building.

While Ian and Vicki are threatened by a Mire Beast, the Doctor and Barbara meet up with the Aridians...who are then ordered to hand them over to the Daleks.

The TARDIS crew's attempts to escape from the Daleks take them to the top of the Empire State Building and a 19th century sailing ship.

The TARDIS lands in a haunted house where the Doctor and his friends are confronted by Dracula and Frankenstein's Monster...and then the Daleks appear.

With Vicki trapped on board the Dalek time machine, the Doctor, Ian and Barbara decide to make their stand on the planet Mechanus.

The Doctor and his friends are taken into the Mechanoid City but their troubles are far from over...especially when the Daleks launch an attack.