Let sleeping dogs lie. (寝た犬は起こしてはいけない。 Neta inu wa okoshite wa ikenai): is the 8th episode of The Ancient Magus Bride anime.
After having been struck and lost conscious, Chise finds herself in the monstrous arms of her teacher. But as the Mage is consumed by rage, Elias let's go of her and starts attacks Cartaphilus' chimera while Ulysse attempt to wake Chise. The Sleigh Beggie dreams about Ulysse's past with Isabel and of her demise before waking up again. As Elias goes on to provoke Cartaphilus by calling out his name after finishing with the chimera but is stopped by Chise while Cartaphilus takes a shot from Renfred. Elias returns to his usual form as both teachers reunite with their apprentices. Cartaphilus recovers however and a chimera made from Isabel appears before them. Chise goes on to threaten Cartaphilus before Blue Flame shows up and teleports them away.
Once safe, the faerie is identified as Will o' The Wisp and he quickly goes on to bicker with Elias before both of them retort to calm Chise down. Blue Flame continues to help Ulysse realise his true nature as a church grim, only to see the dog offering himself as a familiar to Chise. Cartaphilus returns but is unable to prevent the Sleigh Beggie and the Black Dog from forming their pact, leading to Ulysse being renamed into Ruth and him killing "Isabel". Cartaphilus retreats and Renfred along with his apprentice leaves as well. Before Elias and Chise leave together with Ruth, they witness Blue Flame leading the dead souls away.