Spring was the first story in the audio anthology, Circular Time, which comprised the ninety-first release in Big Finish's monthly range. It was written by Mike Maddox and featured Peter Davison as the Fifth Doctor and Sarah Sutton as Nyssa.
It featured the Doctor meeting another Time Lord who had "gone native" on an unnamed world inhabited by an avian species. It was perhaps most notable for its theme of how to construct a valid system of jurisprudence.
to be added
- The Doctor - Peter Davison
- Nyssa - Sarah Sutton
- Hoodeye - Jamie Sandford
- Redklaw - Toby Longworth
- Carrion - Lois Baxter
- Snowfire - Teresa Gallagher
- Zero - Hugh Fraser
- The Doctor mentions jelly babies and his fourth incarnation's scarf.
- Zero is from the Prydonian Chapter of Time Lords, the same chapter that the Doctor belongs to.
- The Council of the Great Mother is a Time Lord organisation.
- According to a 20 November 2006 blog post, Mike Maddox wrote this story based on a short story by Paul Cornell.
- This was the first in a series of stories named after seasons.
- Lord Cardinal Zero's regeneration at the end of this story is the only instance of a Time Lord regenerating into a different species.
- Nyssa suggests the Doctor might be afraid of heights after his fourth incarnation's fatal fall from the Pharos Project's telescope on 1 March 1981. (TV: Logopolis)
- Zero refers to the Doctor's first trial on Gallifrey and his consequent forced regeneration into the Third Doctor. (TV: The War Games)
- Zero sarcastically asks the Doctor if the Time Lords have sent him to stop the creation of the avians' empire or lock them in a tunnel, setting them back over a thousand years. (TV: Genesis of the Daleks)
- The Doctor wakes Zero up by yelling, "Look out, vampires in the Capitol!" (TV: State of Decay)