Dumbledore is at his wits end. He's certain that Voldemort has created horcuxes and that Harry is one of them. However, he has no idea where the others are and can't justify a teacher leading a student to his death. Desperate to find and destroy the horcuxes and to find an alternative to Harry's death, Dumbledore decides to go to the most intelligent person alive beside himself, Grindelwald, for help. He secures his old friend's release on the condition that Dumbledore be responsible for making sure Grindelwald doesn't kill anyone/take over the world/the usual, and on the promise that this is absolutely vital to defeating Voldemort. Grindelwald in turn is promised...IDK, something he wants if he cooperates.

How does this change the course of the books? Does Gellert betray Dumbeldore?