Sam and Dean try to help Castiel recover from Rowena's spell, while searching for Amara who has now grown into a young girl. Rowena tries to use her powers to protect herself from the Winchesters, while Crowley tries to use Amara for his personal gain.
Sam and Dean investigate a series of murders at a local B&B that also happens to be Lizzie Borden's old home. When a man tells them he saw a little girl around the B&B around the time of the murders, the brothers realize Amara may be responsible.
Castiel seeks out Metatron's help to stop the Darkness. However, Metatron is pretty happy with his new life as a freelance videographer for the local news and isn't inclined to help the Winchesters or Castiel.
Claire believes recent murders in town are supernatural and asks Sam and Dean to investigate. However, Sheriff Mills tells the guys that Claire has been getting into trouble lately and has been attacking normal people and accusing them of being monsters.
After dangerous creature is released into an old house, a mother and child are comatose. Sam and Dean find that Bobby and Rufus tracked the same creature so the Winchesters look to the past to catch the monster before any one dies.
Sam and Dean are visiting a small town in Colorado where people are mysteriously disappearing every 27 years. While they are investigating, the boys encounter a pair of hunters seeking revenge on the monster causing the disappearances.