The episode ends on a grim cliffhanger that leaves the Winchesters nearly alone:
His presence is marked by icy mirrors and flickering lights. [S7E22] There Will Be Blood
Sam and Dean discover that the Leviathans are poisoning the human food supply with a corn syrup additive. This additive makes humans lethargic and "tasty" for Leviathans but is lethal to other monsters, such as vampires, who feed on them. The episode ends on a grim cliffhanger that
The Leviathan Edgar arrives to kill the Alpha and "purge" the vampire race. After a tense struggle, Sam decapitates Edgar with the brothers' new "vamptonite"—blood taken from a corn-syrup-dazed human—giving the Alpha a change of heart. Grateful but still hostile, the Alpha hands over his blood and releases a captive boy, Allan, to the Winchesters. Bobby’s Descent The Leviathan Edgar arrives to kill the Alpha
Dick Roman summons Crowley into a devil’s trap to prevent him from helping the Winchesters.
The boys track the Alpha Vampire to a hidden monastery. They attempt to negotiate, warning him that the Leviathans—his supposed allies—are actually planning to exterminate his kind by poisoning their food source.