The Twin Dilemma

As a result of his recent regeneration, the Sixth Doctor suffers from mood swings and violent delusions, culminating in his attempt to strangle his companion, Peri Brown. Realising the threat he could pose to the universe in this state, the Doctor decides to exile himself (and Peri, over her protests), to a remote asteroid named Titan 3. Meanwhile, the mysterious Professor Edgeworth abducts two teenaged math geniuses, Romulus and Remus Sylvest, at the behest of Mestor, the leader of the slug-like Gastropods who have usurped Edgeworth as ruler of the planet Jaconda. Mestor orders Edgeworth to hide on Titan 3, and destroys a pursuing squad of fighters.

The only survivor of the fighter squadron is Lt. Hugo Lang, who crash-lands near the TARDIS. The Doctor saves Hugo at Peri's behest, and he and Peri investigate the asteroid, leading to them being captured by Edgeworth. The Doctor recognises that "Edgeworth" is actually Azmael, a fellow Time Lord and his former tutor. Azmael tries to strand the Doctor and Peri on Titan 3, but unbeknownst to Azmael, his assistant Noma arms a bomb intended to kill them both, and they narrowly escape with their lives.

The Doctor, Peri, and Hugo follow Azmael to the now-desolate Jaconda, where Azmael makes it clear he never intended for them to be harmed, and reveals that Mestor is forcing him to have Romulus and Remus create calculations which will terraform two nearby planets that the Gastropods can settle on. The Doctor, however, realizes that Mestor has lied to Azmael about the nature of his plan, and the calculations will actually cause Jaconda's sun to go supernova, allowing Gastropod eggs to infest the galaxy.

After the Doctor tries and fails to kill him, Mestor announces that he will take over the Doctor's body. The Doctor tries to goad Mestor into doing this, but he instead takes over Azmael. The more experienced Azmael manages to briefly retake control of his body and initiates a regeneration, but since he has used up his entire regeneration cycle, this has the effect of killing both himself and Mestor, though Azmael and the Doctor make amends before the former dies. Hugo decides to stay on Jaconda and become its new ruler, while the Doctor agrees to return Romulus and Remus to their parents. Peri still has doubts about the Doctor's new personality, but he reminds her that "I am the Doctor, whether you like it or not!"

The Doctor is unusually violent at the start of this episode, even attempting to strangle Peri.[3] The intention was to create a Doctor that was initially unlikeable, but would gradually reveal a kind-hearted soul (glimpsed in Revelation of the Daleks). This was also intended to be a contrast to the instantly likeable Tom Baker and Peter Davison Doctors. However, in later interviews, director Peter Moffatt said that the original idea was merely to have the Doctor in a much more energetic state than he was during the Fifth Doctor's début story Castrovalva. Colin Baker said during a 2003 documentary celebrating the series' 40th anniversary that "the idea was that over the many, many years I would be playing the part, the outer layers would gradually peel away, revealing the kind-hearted soul."

At least one aspect of Steven's original script featured the Jaconda and Gastropods being dropped totally early in the fourth episode without resolution to the plot, with the final battle taking place in another dimension against a being called Azlan who was controlling Mestor all along.

The cat badge worn by the Sixth Doctor on his lapel for this story was handmade and painted by Suzie Trevor and purchased for the programme from a specialist badge shop in central London. For each subsequent story, the Doctor was to wear a different cat badge to symbolise that he was a "travelling cat of different walks."

Besides being adjusted for the new Doctor, the opening credits underwent additional modifications with this episode. A prism-colour effect is added and the series logo takes on a somewhat bluish hue (which also results in it appearing slightly curved in comparison to the version introduced during Tom Baker's era). The theme music remains the same version as that introduced in 1980. Prior to this, the opening sequences of the Second, Third, Fourth, and Fifth Doctor eras had incorporated a still photograph of the lead actor. For the Sixth Doctor opening this was changed to using two photographs – one of the Doctor with a smile which changes to a second image showing the Doctor grinning. This limited animation would continue with the opening sequence for the Seventh Doctor.

Where the previous serial, The Caves of Androzani, is frequently cast among the very best of all Doctor Who stories, the fandom often holds this serial the polar opposite, commonly regarding it as one of the very worst serials in the history of the series.[2][3] The review of the story in Doctor Who: The Television Companion describes The Twin Dilemma as "painful to watch", describing the Doctor's erratic behaviour as "forced and artificial, and succeed[s] only in alienating the viewer." The review also argues the script "leaves much to be desired" and that the direction is uninteresting, giving the whole story "a rather tacky, B-movie feel to it".[8] In SFX #150 new series producer Russell T Davies cites this story as "the beginning of the end" of Doctor Who. Tat Wood and Lawrence Miles, reviewing the story in the book About Time, noted that the divide in quality between The Caves of Androzani and The Twin Dilemma "felt wrong at the time, and still feels wrong now".[2] They also asked "How could anyone have thought that this story, of juvenile space monsters, meaningless plans and never-ending cop-outs, was ever workable?".[2] In his review for Radio Times, Patrick Mulkern gave the serial a negative reception, stating: "If The Twin Dilemma is individually a disaster, it also establishes the opening titles, the Doctor’s clothes, his behaviour and sniping banter with Peri – all part of an unpleasant shift in tone that would permeate and eventually poleaxe the era. How did Nathan-Turner and Saward think that this approach might be in any way acceptable?"[9] A 1998 poll by Doctor Who Magazine ranked the serial the second worst of all time (the Children in Need special Dimensions in Time was ranked lowest), while a 2003 poll by fansite Outpost Gallifrey ranked it worst of all, below even Dimensions in Time. In 2009, another Doctor Who Magazine poll of the 200 stories produced up to that point saw the serial finish in last place again, along with finishing last in every single age group that voted (although Dimensions in Time technically scored lower, it was no longer included in the main poll due to its lack of canonicity within the series and was instead placed in a spin-off section). A similar poll in 2014 placed the story in last place once again.[10]

Wikiquote has quotations related to Sixth Doctor.

• The Twin Dilemma at BBC Online