Dean and Sam read about two bizarre death cases in Prosperity, Indiana, and they head to the town to investigate. They try to find something common in the cases when the owner of a construction company is murdered by a nail gun that had operated without available power. The Winchester brothers discover that the three victims were working on a project involving the construction of a mall with the investor Don Stark. They visit the businessman and find that his wife Maggie has separated from him, believing that he had a love affair with his secretary. Furthermore, they discover that Maggie is a powerful witch and Don is a powerful warlock. Meanwhile, a leviathan is hunting down the Winchester brothers and waiting for them in their hotel room.