It wasn't hard for Zach to figure out his girlfriend was a witch after she swapped their bodies. He guessed she was his ex-girlfriend now -- after all, he didn't have much interest in continuing the relationship like this. he felt so foreign in her skin that he barely wanted to leave the house or talk to anyone. While digging through the things in her house, he found many of the spellbooks she had used. There were warnings, saying they'd only work if you had a body attuned to magic. Zach figured it was a long shot, but when he cast a simple spell to make fire in his hands, he was shocked it actually worked. He thought about it. Maybe he always had a little magic in him, or maybe now that he had his girlfriend's body, he had her magic too. That meant he could probably figure out the magic to swap back. Of course, if he didn't swap back, he had access to real, live magic. The latter seemed much more appealing, especially if she was now powerless in his body. This was going to be fun.