Midnight Over Sanctaphrax is a children's fantasy novel by Paul Stewart and Chris Riddell, first published in 2000. It is the third volume of The Edge Chronicles and of the Twig Saga trilogy; within the stories' own chronology it is the sixth novel, due to the Quint Saga trilogy that was published later.
In trying to save his father Cloud Wolf from the vortex he was trapped in during the Mother Storm, Twig learns that Sanctaphrax is about to be destroyed by the Mother Storm which will replenish the waters of the Edge by returning to Riverise, a legendary waterfall from which all life came from. He and the crew of the Edgedancer are then scattered across the Edge by the collapse of the vortex, with no memory of the voyage into open sky. Pieces of the destroyed Edgedancer rain down upon Undertown, killing and injuring many. Among the dead are 3 Leaguesmen. A dazed Twig is rescued from the Stone Gardens by the Professor of Darkness and taken to Sanctaphrax where he is made the new Sub-Professor of Light and kept safely away from the other academics. On recovering from his condition, Twig makes a young sub-acolyte, Cowlquape (a boy who would have been forced to leave Sanctaphrax because his father, the one paying for his attendance at school, was among the leaguesmen killed by a piece of the Edgedancer), his "apprentice" (thus saving him from being cast of out Sanctaphrax) and with his help they set off to find the missing crew and discover the memories that could save the Edge from destruction. They travel across Undertown, the Mire (in a ship), the Deepwoods and Riverrise. They find 3 of the crew in Undertown, 1 in the Deepwoods, and finally the Stone Pilot, who is the only one who retained her memory of what happened in the Weather Vortex (due to her Stone Pilot's Hood). She tells Twig that his father became a piece of the Great Storm and that Sanctaphrax needs to be released before the Mother Storm itself reaches it so the storm can reach Riverrise so life in the Edge goes on. Twig and Cowlquape fly to the Stone Gardens, and then run to Undertown, where all the academics were evacuated from Sanctaphrax, including the Professor of Darkness, who won't let Twig and Cowlquape release Sanctaphrax. He pushes Twig from the platform and tries everything to stop Cowlquape. He even makes Cowlquape the Supreme Rector, but Cowlquape releases Sanctaphrax, that flies away with the Professor of Darkness. The two explain everything to the academics and the Undertowners. The Mother Storm reaches Riverrise. In the meanwhile, a giant stone is growing in the Stone Gardens, the academics take the stone and it becomes the new Sanctaphrax, ruled by Cowlquape. Twig gets a new sky ship and the book ends with him leaving to venture towards Riverrise to recover his crew, saying goodbye to Cowlquape, who wishes Twig luck. This is the last book of the Twig Saga.