Grace has a weird life. Even before she accidentally finds a werewolf that's not a werewolf on the way home from work, she has a weird life. If it stopped at ghosts and werewolves it wouldn't be so bad. At least the people who hunt these things know how to deal with those.
Nate's had an entire life of supernatural crap, but he's got no idea why Grace keeps exploding in white light every time she's in trouble. But, surprisingly, they make a good team. If there's suddenly a little more mystery in his life than he'd like it's worth it. Even when it's a lot more mystery, and witches, and psychics, and just mess it's still worth it.