Dean helps Jenna, the nurse he met after the Darkness fell, get back home safely, but she soon falls into dangerous hands. Meanwhile, Sam deals with a town infected by a mysterious and deadly gas that is turning the locals into monsters.
Rowena tries to consolidate her power to protect herself from the Winchesters, while Sam and Dean search for a missing baby connected to the Darkness. Meanwhile, Castiel struggles to heal; and Crowley tries to find a way to use the Darkness for his own 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 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. Meanwhile, Crowley loses his hold on Amara.
Sam is shocked when his imaginary childhood friend, Sully, makes an unexpected appearance. Sam tries to understand why he is seeing Sully now. Even more surprising, Dean can see him too. Flashbacks reveal young Sam's friendship with Sully and why he needed him.
Amara unleashes her power on local townspeople and issues a shocking challenge. Dean tries to better understand the hold Amara has on him, while Sam and Crowley come up with a plan that could have disastrous consequences.
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.
Dean, who hopes to find a weapon powerful enough to defeat Amara, convinces Lucifer to send him back in time to 1944 to the ill-fated submarine mission that sunk the Hand of God. Meanwhile, Lucifer continues his charade with Sam as they wait for Dean's return.
A dangerous creature is accidentally released into an old house where it attacks a mother and her child, leaving them both in a coma. Sam and Dean learn that Bobby and Rufus once tracked the same entity, so they look to the past to come up with a plan to catch the monster before anyone dies.
Sam and Dean battle a pair of werewolves who captured two victims. One of the werewolves shoots Sam, and Dean tries gets his brother and the victims to safety but learns that a pack of werewolves are hot on their trail, hoping to kill them all.
In a small town in Colorado, mysterious disappearances happen every 27 years. Sam and Dean head to the town to investigate and meet two hunters who have a personal vendetta against these once-in-a-generation monsters.
Amara unleashes a dark fog on a small town that causes everyone to go mad. Dean and Sam realize this is a stronger version of the original black vein virus Amara previously unleashed. They team up with the sheriff to protect the town but discover their old remedy no longer works. Meanwhile, Chuck returns with an interesting proposal.
Photo Credits: Michael Courtney/CW; Sergei Bachlakov/CW; CW; Jack Rowand/CW; Bettina Strauss/CW; Colin Bentley/CW; Netflix; Pop TV; Robert Viglasky, Hartswood Films; Fred Hayes/Disney+, Fox, PopTV; Bettina Strauss/Netflix; Nicole Rivelli/Amazon, Netflix, Frank Masi/Apple, Disney, Jasper Savage/Hulu; Diyah Pera/CW