Sam (Jared Padalecki) and Dean (Jensen Ackles) are once again on the FBI's "Most Wanted" list when two Leviathans clone the brothers and go on a killing spree. The subject of a nationwide manhunt, Sam and Dean need to drop off the grid so Bobby (Jim Beaver) sends them to Frank Deveraux (guest star Kevin R. McNally), a quirky surveillance expert, for help. Meanwhile, Bobby continues to search for a way to kill the Levianthans, or at least slow them down, so the real Winchesters can stop their evil doppelgangers.