On his 16th birthday, Mark's brother, Thomas, introduces him to the dark family secret and hands him the Chronicle of the Black Tower, a different world ruled by an eerie creature - the Gryphon. But how is the chronicle related to their father's death?

Against his mother's will, Mark tries to find a way back to the world of the Black Tower in order to save Memo. Meanwhile, Becky tries to find out if the contents of the Chronicle really exist or if Mark is suffering from hallucinations.