Twilight Canyons is the possible name for an unfinished novel by Terry Pratchett. The only mention of this book that can be found in the Discworld novels is in the afterword to The Shepherd's Crown that was written by Rob Wilkins:
'We will now not know how the old folk of Twilight Canyons solve the mystery of a missing treasure and defeat the rise of a Dark Lord despite their failing memories,'
The story was one of several that were in various stages of planning by Terry Pratchett; two years after his death in 2015 one of his final wishes was to have the hard-drive of his computer crushed by a steamroller and this was carried out rendering the remnants of his works permanently unreadable.
Allegedly a sample of what was written by Terry Pratchett for this story was read out by Rob Wilkins at a 2016 Discworld Convention and then promptly shredded after he had finished.
The fourth episode of the 2021 TV series 'The Watch,' based very loosely on the City-Watch series of novels, is named 'Twilight Canyons.' Simon Allen, the showrunner of the series, was apparently present at the convention where a snippet of the book was read out to the attendees. Due the rather drastic amount that The Watch series differs from the source material of the novels it is uncertain how much this depiction of Twilight Canyons resembles the original.
In the show Twilight Canyons is a retirement home located in Ankh-Morpork. Some of the residents of the home seem to suffer from memory loss or dementia to varying degrees naming all visitors 'Michelle.' There is also a 'Displacement Spell' over the home which prevents violence within the walls; if anyone in the building should try to fight this triggers the spell which forces the fighters to dance together whilst music plays.