Mark Zimmermann would love to celebrate his 16th birthday with his new crush Becky. Instead, his brother Thomas is taken to the eerie world of the Black Tower, ruled by a merciless beast, the Gryphon. Mark musters all his courage and embarks on an epic rescue mission. Together with his work colleague and heavy metal expert Memo, he travels deep into the mining plains of the Black Tower. At the same time, Becky tries to find out if this other world really exists. When she learns the truth about Mark, his family and the Black Tower, Mark's time has almost run out. With every adventure he experiences in the other world to get one step closer to his brother, a change takes place in Mark, which he will soon find difficult to control.