A Doorway Into Ultra — Susannah J. Bell

When a missing child is returned without her memory, only her abductor knows who she is �" and who she isn't.

Claire Halward disappeared as a child, last seen running up a hill before being struck by “something dark.”

Found in the same spot seven years later, her mother Karin is delighted to have her back. But the reunion doesn't go well. Karin struggles to connect with Claire and Claire's father Nick knows Claire is not Claire, despite accurate DNA tests.

Claire herself has no memory of these parents nor of the house they live in. She has no memory of herself. She remembers a twin sister she doesn't have and dreams of her. Her body is covered with inexplicable scars and soon she begins to add to them.

Watching the disintegrating family is a man with silver-blue eyes. Unable to sleep, plagued with nightmares, struggling with the residual effects of machine-administered drugs, John Fox is the only man on Earth who knows the truth about Claire.

And then she runs away to find him.