 Every ten years, The Assassins Guild and The Thieves Guild must each give an offering to a supernatural being called The X-Ternal, in exchange for power. When it comes to be Gambit s brother, Bobby, who has to offer the tithing this time, he comes up missing. The Assassins Guild want to exchange him for Gambit, so he can finally come face to face with the woman he left at the altar 10 years before.