Dean starts seeing Castiel in a way that he never imagined possible. After Dean receives some news that stresses him out, him and Cas both share a strange moment in the Impala which leads to the hunter and the angel both experiencing feelings for each other. Dean is also determined to do whatever it takes to get Cas' angel grace back.
Lucifer is back. At first, Sam thinks it is another hallucifernation but he soon realises that it is anything but imaginary. Even though Lucifer's first intentions are to completely mess with Sam's head, his true feelings start to show and Sam doesn't know how to react. What used to be flirtatious remarks of sarcasm from Lucifer soon evolves into reality.
While Sam and Dean seem to be having separate things going on with their love lives, they also need to discover what's going on when almost everyone they know start returning from the dead.