It was a marginal victory for the PCs, or perhaps a draw. Garrett had more hit points at the end of the battle than at the beginning, but the PCs managed to get the artifact dagger Weeping Wounds and get away. I'm pretty sure I misplayed, but it's also true that the PCs played extremely well.
However, there is a silver lining to the cloud: Prolix (who has the dagger) and Turok are alone together, miles away from the others. Prolix is very low on spells. Currently, Turok is size large, while Prolix is a normal-sized gnome. And Turok is dominated by the vampire.