Ep 21. Let It Bleed

Sam and Dean continue their mission to collect the three key ingredients for the weapon that will defeat Eve. The first ingredient is the blood of a Purgatory monster, so they decide to capture a Leviathan and bleed it, but it's not as simple as they thought. Meanwhile, Bobby tries to help the brothers find a way to defeat Eve, but he is struggling with his own demons as he grieves the loss of his wife. Elsewhere, a familiar face returns to help the Winchesters, but it may come at a steep price. As the clock ticks down to the end of all life on earth, Sam and Dean face some of their toughest challenges yet in this intense episode of Supernatural.