Winter was the fourth story in the audio anthology, Circular Time, which comprised the ninety-first release in Big Finish's monthly range. It was written by Paul Cornell and featured Peter Davison as the Fifth Doctor and Sarah Sutton as Nyssa.
It was set within the last few moments of the Fifth Doctor's life, as he battles the Master for control of his regeneration — meaning that most, but not all, of the narrative takes place in the Doctor's mind. This also meant that the events of this story were contained within the finale of TV: The Caves of Androzani, and revealed the origins of the visions within his head as he regenerated.
Many years after their travels together have ended, the two friends meet again in the strangest of circumstances.
The Fifth Doctor heads out into a blizzard with a mysterious woman. Far away, in another time and place, Nyssa tells Lasarti about a dream she had, reminding her of a time she was with the Doctor. Her dream had Tegan, Adric, the Master, the Doctor and others she couldn't quite recognise. She asks Lasarti to let her use his machine at the hospital to see the dream more clearly. The Doctor and his "wife" find a knocking noise in their barn but decide not to investigate further.
The Doctor encounters Nyssa in his dream but she exclaims that it is he who is part of her dream. He invites her into a parlour in a farmhouse he supposedly inhabits with his human wife and they have a chat, trying to discern who is real and who is the dream/illusion. He, however, has no recollection of her or anything from his life, convinced he is a human who has lived in this house all his life. Just then he hears a noise coming down the stairs and Lasarti has entered the dream. Nyssa decides to test whether she is dreaming or not by switching off the device. She does, yet they are both still in the Doctor's dream and Nyssa is confused. She asks him a series of questions that makes him begin to realise he isn't sure about anything, such as not remembering his wife's name or the fact that his children Adric and Tegan are not who he claims them to be as Nyssa continues to remind him. Panicking, they hear a malicious laugh coming from outside and go out into the blizzard to find the source. Nyssa recognises the laugh as belonging to the Master and tries to convince the Doctor but the Doctor rejects this, trying to convince himself that he is human. Nyssa tries to jog his memories and convince him that this isn't real, reminding him of Adric, herself, Tegan and others as well as his heritage as a Time Lord, which he vaguely starts to remember. They go into the barn and see a coffin vibrating and Nyssa manages to convince the Doctor to go inside, which turns out to be the Doctor's mind envisioning a zero cabinet, which once inside he reverts back to his old self and explains what's happening to Nyssa. He then asks her and Lasarti to burn everything around them down as he is a traveler who never stays put, which is what the projection is desgined to do, lull him into a false sense of security and this interference by the Master was to block his mind from reaching out across time and space to former companions to help him regenerate. The Doctor then tells Nyssa to help him to the edge of the forest to find the Watcher while Lasarti burns everything and the Doctor's "wife" is revealed to be Kamelion, who thanks Lasarti for helping it finally resist the Master and die, and that it was it that tried to save the Doctor's mind by helping him remember Adric and Tegan by projecting them as children to help him remember since it was the key linking the Doctor's and Master's minds. It finally reveals that once it disappears the connection between the Doctor's mind and the Master's that it has been keeping will disappear.
The Doctor and Nyssa struggle to the edge of the forest, but the blizzard disappears as Kamelion vanishes and he manages to find the Watcher. He thanks Nyssa for her help and merges with the watcher, preparing to regenerate again.
Nyssa and Lasarti discuss their recent adventure and she tells him the Doctor's last moments, how he took her hands and kissed her on the head and after thanking all of his previous companions surrounding him in his mind and ran back into the Watcher's figure and regnerated. The two reflect on their own children and Nyssa is thankful for her time with the Doctor, even if their final interaction was through a dream, unsure if she will ever see him again.
- Nyssa points out that aspects of the Doctor's farmhouse resemble the TARDIS like the hat stand and Nyssa's bedroom.
- The Doctor thinks his wife is named Peri or perhaps Kamelion. It does indeed turn out to be the latter.
- Nyssa mentions the Doctor's people, the Time Lords, but doesn't explicitly name them.
- The Master hates being alone.
- There are mentions of the Fifth Doctor's former companions Adric, Tegan Jovanka and Turlough as well as his current companion Peri Brown.
- Nyssa is married to a man named Lasarti. They have an infant daughter, Neeka.
- The Doctor tells Nyssa and Lasarti that he is dying of Spectrox toxaemia.
- The Doctor compares regeneration to the Buddhist concept of reincarnation, stating that "Each life creates the next."
- Time Lords have the ability to make mental contact with others across time and space.
- There is an existence (albeit only a mental one) for a Time Lord's departing incarnation within the act of regeneration.
- Though Paul Cornell and Mike Maddox share the writing credit on the Circular Time anthology, this story was written by Cornell alone. Cornell has referred to the story as "a weird fanservice thing."
- In spite of the fact that he remains unseen throughout, this is the first Fifth Doctor audio drama to feature the Master as a villain. He would later appear in AUDIO: Smoke and Mirrors and AUDIO: And You Will Obey Me.
- As it takes place during his regeneration into his sixth incarnation as depicted in TV: The Caves of Androzani, this is the final audio drama, chronologically speaking, to feature the Fifth Doctor.
- There's an in-joke when Nyssa mentions the Master while in the Doctor's mind/dream and the Doctor, still thinking he's human, asks if she too watches his adventures on the television twice a week and that his kids love it. This is an in-joke to the program itself, which was broadcast twice a week during Peter Davison's run as the fifth Doctor,
- Nyssa and Lasarti help the Doctor into a recreation of the Zero Room in his mindscape. (TV: Castrovalva)
- The hallucinations of former companions experienced by the regenerating Fifth Doctor during the closing moments of The Caves of Androzani are revealed to be representations of his attempts to make mental contact with them across time and space and get their support in regenerating.
- The Master uses Kamelion's lingering connection to the Doctor's TARDIS to try to prevent the Fifth Doctor's regeneration into the Sixth Doctor. (TV: The Caves of Androzani)
- The Doctor says "Is this death?" and murmurs that his regeneration "feels different this time." (TV: The Caves of Androzani)
- The Doctor and Nyssa encounter the Watcher in his mindscape and the Doctor merges with him to complete the transition into his next incarnation. (TV: Logopolis)
- The Doctor says that his next incarnation will be very colourful, a possible reference to the Sixth Doctor's patchwork coat. (TV: The Twin Dilemma, et. al)
- Kamelion tells Lasarti that the Doctor dies each time he regenerates. The Tenth Doctor would later make a similar comparison when contemplating his own upcoming regeneration. (TV: The End of Time)
- Later in her personal timeline, Nyssa would encounter the Fourth Doctor in 3488 (PROSE: Asylum), rejoin the Fifth Doctor as one of his companions (AUDIO: Cobwebs), and eventually become trapped in the small universe of E-Space, cut off from the Doctor forever. (AUDIO: The Entropy Plague) From the Doctor's perspective, these events had already taken place. However, to preserve the Web of Time, the Doctor doesn't tell Nyssa about these events.
- Nyssa and Lasarti would later have a son, whom she named after Adric. (AUDIO: Heroes of Sontar, Prisoners of Fate)
- The Doctor tells Nyssa that both Tegan and Turlough have left the TARDIS. (TV: Resurrection of the Daleks, Planet of Fire)
- The Doctor uses a zero-cabinet in his mind to help aid his regeneration. He also used this when he regenerated from his previous incarnation. (TV: Castrovalva)
- The spectrox poison is breaking down his nervous system. (TV: The Caves of Androzani)
- The Doctor, reaching out to Tegan, is glad she is happy to do anything to help him, and he says "Brave heart, Tegan", a line he often told her. (TV: Earthshock, Enlightenment, et al.)