Stake Land

After Willie dies and Belle is kidnapped, Martin and Mister discover that, despite managing to stake him, the vengeful (since his teenage rapist son was slain by Mister) religious fanatic Jebedia Loven (Michael Cerveris) who they left for dead, has come back as a vampire.

They discover Belle is now turning into a vampire and Martin is forced to kill her, knowing her unborn child will die too.

Soon after, Mister deserts Martin to go solo, leaving Martin to travel alone until joining up with the owner of a diner.

Thanks ND Woods!