Cassidy is Abby

All the things Abby knew about the animatronics came from Cassidy, who was possessing her all this time. Now that Cassidy got out, William made a dark ritual that turned the animatronics, their spirits and even Michael into creatures of the night.

Abby, Cassidy, Vanessa and Gregory will have to face them all and search for ways to end William.
The Golden Freddy's spirit (the blonde boy) called Ethan Afton and Michael are after Cassidy and Abby because they want to turn them into monsters too.

The group have little time to find a solution and Cassidy, the most powerful among the heroes, already has her hand full with Ethan (Golden Freddy) and Puppet, two of the most powerful animatronics. Not only them, but William too.

Will Cassidy be able to save her friends and destroy William Afton?