Kate saved him from dying (Again? He's a vampire. She has no idea.) and Joce saved her from dying (by killing her). When she awakens as a vamp, she's not sure it's an even trade.

Joce Magli, vampire and Knight Protector, thinks of humans as food and nothing more. Until he meets Kate—doctor, savior, and most delicious woman he's ever tasted. And don't get him started on all her lush curves... She is his and when circumstances force his hand—when it becomes a choice between life and death—he claims her forever. Kate is his fire, his vampire mate, and then she's actually on fire and there is the half-God trying to strangle her and... yeah, it's been a bad day.

And it's only going to get worse.