The author has stated that the end was inspired by The Turn of the Screw (https://en.m.wikipedia.org/wiki/The_Turn_of_the_Screw https://en.m.wikipedia.org/wiki/

The author has stated that the end was inspired by The Turn of the Screw (https://en.m.wikipedia.org/wiki/The_Turn_of_the_Screw https://en.m.wikipedia.org/wiki/The_Turn_of_the_Screw) so my feeling is: you’re not really supposed to know. I’ve always interpreted the ending as the dissolution of the main character’s persona and the return of Phaedrus.