San and Dean go looking on the black market for the blood of "a most holy man", and become involved trying to recover the stolen skull of St. Peter.

Sam and Dean get a lead on the last item they need to open the rift: the Seal of Solomon, at a Men of Letters chapterhouse in Rhode Island. They soon discover something else: a woman imprisoned there for over 80 years. Meanwhile, Asmodeus teaches Ketch his place in the demon prince's hierarchy.