The brothers gear up for a fight, but Charlie contacts them when her girlfriend disappears.
The brothers realize that Billie is making people disappear who have been brought in from an other world, or have been brought back to life.
They rally everyone up, including Bobby in the lighthouse and go try to rattle Billie, but she tells them she is dying and will send everyone away.
Sam goes to help Jack, who died in The Empty, but was brought back to life for some reason.
Everyone starts to disappear from the lighthouse, leading them to believe something else is going on than either of them understand.
The fight with Billie heats up with Cas and Dean fighting their way against her, but she manages to get her weapon back and they run away and hide.
Castiel realizes that the only way to save them is to get the entropy to come after them, leading to a devastating scene when Cas reveals that saving Jack meant he had to make a pact to die when he was happy.
He told Dean he loved him and took Billie out of the equation.
Sam and Jack realized everyone was missing from the world.