Structurally, the season retread season 18's formula of including a trilogy of stories bound together by an overarching theme. In this instance, the tripartite tale involved Turlough's attempts to kill the Doctor at the behest of the Black Guardian.
All episodes — Season 20
S20 E1Arc of Infinity (1)
Jan 3, 1983625 min
On Gallifrey, someone on the high council is perpetrating a treasonous act - transmitting the Doctor's bio-extract from the space/time matrix to an anti-matter being. On Earth, two English lads spend their last night in Amsterdam sleeping i
S20 E2Arc of Infinity (2)
Jan 5, 198325 min
With an anti-matter being trying to enter the universe through the Doctor, risking the destruction of everything, there is only one clear course of action for the High Council of Time Lords to take: execute the Doctor. Meanwhile, Tegan arri
S20 E3Arc of Infinity (3)
Jan 11, 198325 min
Something seemed amiss about the Doctor's execution, so the Castellan has Commander Maxil discreetly but fully look it. Meanwhile, as the Doctor meets the anti-matter being inside the Time Lord Matrix, Tegan and her cousin's friend run afou
S20 E4Arc of Infinity (4)
Jan 12, 198325 min
The High Council creates a distraction so the Doctor and Nyssa can find Omega on Earth and prevent his reentry into our universe.
S20 E5Snakedance (1)
Jan 18, 1983625 min
Tegan steers the TARDIS to the planet Manussa, without meaning to - but why? And is it a coincidence that the planet is about to celebrate the 500th anniversary of the expulsion of the insidious Mara?
S20 E6Snakedance (2)
Jan 19, 198325 min
The Doctor talks to Ambril and Chela to try and stop the 500th anniversary celebrations. A possessed Tegan finds herself in Dugdale's Hall of Mirrors to where she summons Lon. The Doctor and Nyssa return to the caves.
S20 E7Snakedance (3)
Jan 25, 198325 min
The possessed Tegan and Lon try to find the whereabouts of the Great Crystal. The Doctor finds himself in prison, with only Nyssa to try and get him out. Chela tells the Doctor tales of Dojjen.
S20 E8Snakedance (4)
Jan 26, 198325 min
The Doctor and the original snakedancer Dojjen work to rid the planet of the Mara.
S20 E9Mawdryn Undead (1)
Feb 1, 19836.625 min
The Doctor discovers a starship trapped in a time warp over Earth. Meanwhile, public schoolboy - and secret alien émigré, Turlough, learns he can have that which he most desires, in return for the murder of the Doctor...
S20 E10Mawdryn Undead (2)
Feb 2, 198325 min
The TARDIS lands on Earth six years out of date, stranding the Doctor in 1983 while leaving Tegan and Nyssa to look for him in 1977. Both parties also encounter former companion, Brigadier Lethbridge-Stewart, though curiously, he has no mem
S20 E11Mawdryn Undead (3)
Feb 8, 198325 min
Mawdryn and his eternal mutants reveal the truth: they are exiles, they are in pain and need the Doctor's future 'lives', as afforded by each of his remaining regenerations.
S20 E12Mawdryn Undead (4)
Feb 9, 198325 min
As the Doctor's ethics are challenged and the two Brigadiers finally meet, Turlough plots with the Black Guardian to bring the Time Lord down once and for all...
S20 E13Terminus (1)
Feb 15, 19836.225 min
Deep space, some time in the future. Still following the Black Guardian's orders, Turlough sabotages the TARDIS, forcing an emergency fusion with an apparently deserted starship. But the ship is headed for the notorious plague colony, Termi
S20 E14Terminus (2)
Feb 16, 198325 min
The Doctor's party remains divided and scattered as the immense transport docks at the Terminus space station, which turns out to be a leper colony at the exact centre of the known universe. As they find their way around and investigate, Ny
S20 E15Terminus (3)
Feb 22, 198325 min
Since the Doctor's party represents neither lazars nor handlers, they're presumed to be investigators, which is enough to spark the disgruntled Valgard into challenging Eirak over leadership of the handlers. Meanwhile, as the giant, dog-lik
S20 E16Terminus (4)
Feb 23, 198325 min
In attempting to reopen a doorway into the TARDIS, Turlough activates Terminus' automated fuel-jettisoning sequence. The first time this sequence was engaged, it flung its first of two massive loads of unstable fuel into the distant past, p
S20 E17Enlightenment (1)
Mar 1, 19836.825 min
After receiving a warning from the White Guardian, the Doctor initially believes the TARDIS has landed aboard an Edwardian clipper ship - but all is not as it seems. While the time travellers are caught up in the omnipotent Eternals' race f
S20 E18Enlightenment (2)
Mar 2, 198325 min
Captain Striker and his officers reveal themselves to be Eternals, mind-reading creatures who live outside of time and who require Ephemerals (humans and other "time dwellers") to relieve them of their emptiness. They race against other Ete
S20 E19Enlightenment (3)
Mar 8, 198325 min
Turlough's panic puts him aboard a pirate ship where Captain Wrack uses his presence to invite all the other captains over for dinner. She's been picking off a few of her greatest rivals in the race and now sees an opportunity to clear the
S20 E20Enlightenment (4)
Mar 9, 19836.625 min
Tegan isn't aware she been outfitted with a device to destroy Captain Striker's ship. While the detonation will merely slip the indestructible Eternals back into the realm of eternity, nothing nearly so elegant or as tidy awaits the Ephemer
S20 E21The King's Demons (1)
Mar 15, 19835.625 min
In 1215 at the castle of Ranulf Fitzwilliam, son Hugh is jousting on a matter of honor against Sir Gillis Estram, the champion of King John, when the TARDIS appears. The Doctor, Turlough and Tegan are immediately hailed as demons and welcom
S20 E22The King's Demons (2)
Mar 16, 19835.525 min
England, 1215. With the historic signing of the Magna Carta supposedly only days away, the Doctor is startled to find King John apparently intent on provoking civil war - and seemingly in two places at once...