Galaxy Brain is the 12th episode of Season 15. It aired on March 16, 2020.


Dean Purgatory Blade.png There was something about being there... It felt pure.

This episode summary is an official CW press release. It may contain errors.

Sam and Dean respond to a frantic call and together along with CastielJack, and Jody Mills (guest star Kim Rhodes), assist in an extraordinary and heartbreaking rescue. Billie (guest star Lisa Berry) surprises everyone with a visit to the bunker.


Merle says that, despite not caring about Kaia being safe, the mission was a success. When Sam asks her if God didn't sense anything, she replies that, if that happened, they all would be dead. At that moment, she is promptly stabbed by Billie's scythe, to the shock of Team Free Will. As Merle disintegrates, Billie justifies her action by saying Merle failed to do her job by keeping Jack in line and that their team is only as strong as the weakest players, so Merle had to go. Billie tells the group that the difference between them is that she sees the big picture and understands that one life means nothing in the grand scheme of things. Billie reveals that the Bad Place is not the only world that's dying but instead that all of the worlds are dying except for theirs. Castiel realizes that God is behind this which Billie confirms, stating that God has been busy extinguishing galaxies and wiping the slate clean "for the end."

Wanting answers, Sam questions Billie on her own endgame, pointing out that they don't really know what she's up to besides that she said Jack will supposedly kill God. Sam asks what her plan is exactly and Billie responds that as a reaper, she believed in the rules until Castiel killed her. Billie goes on stating after she became Death, she inherited Death's knowledge and library containing books with the ultimate fates of everyone, including God. The group are shocked God has a book too, as Billie states that everything dies in the end the books write themselves rather than be written by God. To keep the world going, God had no choice but to build himself into the framework of it which is God's only weakness. Billie reassures them that not even God can read what's in his book unless she lets him. Billie reminds Dean of his time in the library and how she told him he had work. She then reveals that Jack, Sam and Dean are all in God's book and their destiny is to be the messengers of God's destruction, something that shocks them.


Main Cast

Recurring Cast

Guest Stars


  • Sandra Ferens as Merle
  • Nicco Del Rio as Radio Shed Clerk
  • Amy Waugh as Radio Shed Customer

Featured Supernatural Beings



  • This is the second time Robert Berens and Meredith Glynn collaborated to write an episode with The Future being the first one.
  • This is the first time Castiel sees Billie as the new Death.
  • This is the first time Jody has been to the Men of Letters Bunker.
  • It is confirmed that Jack still has no soul as of this episode.
  • God has started destroying other worlds.
  • While on Earth 2, God displays images of the Sam on Demon Blood killing his brother and another Dean's failed attempt to kill his Lucifer with the Colt.
  • It is revealed Kaia survived her wound, as her counterpart left materials to do so.
  • Jack is briefly seen glancing at the Winchesters' initials carved into the table and touching Mary Winchester's in particular.
  • This is the first time Castiel and Jack interact with Jody.
  • This is the first time Jack meets the Alternate Kaia.
  • It is revealed when Amara invaded the bunker that the warding was not completely repaired. Merle calls the current warding "good enough warding," but not the "cosmic grid stuff" it had been before. She also states that the old warding cannot be fully repaired.
  • The first time Billie is seen killing someone.
  • Billie states that God has a book in Death's Reading Room as God has woven himself into the fabric of the universe in order to create harmony between the worlds and for his Creation to live on after his demise. Billie calls this God's only weakness and only states that the book shows that the Winchesters and Jack are responsible for God's ultimate destruction.
  • Billie reveals that no being, not even God, can see their books in Death's Reading Room unless she lets them.
  • This episode marks the first on-screen use of Death's Scythe by an incarnation of Death. Previously, it was only used on-screen by Alastair and Dean in On The Head Of A Pin and Brother's Keeper respectively.
  • The "failed spin-off" comment God makes during his monologue is in reference to Supernatural: Wayward Sisters. Writer Robert Berens tweeted after the episode "The arc of S1 of Wayward Sisters was always going to be broadly Dark Kaia vs the WaywardSisters, culminating in Kaia’s rescue and Dark Kaia’s tragic defeat. I always wanted to make that death right. But with limited real estate on #Supernatural I had resigned myself to Kaia just being dead. It was only by embedding it in S15 stories (Chuck, Jack’s return to the Bunker, Billie’s plan) it felt like it was possible to tie that loose end in a relevant and appropriate way."
  • In the episode the store is called "Radio Shed" this could be a pun based on "Radio Shack"



Behind the Scenes


Promotional Pictures


Supernatural 15x12 Promo "Galaxy Brain" (HD) Season 15 Episode 12 Promo - Moves to Mondays

Supernatural 15x12 Promo "Galaxy Brain" (HD) Season 15 Episode 12 Promo - Moves to Mondays

Supernatural 15x12 Sneak Peek "Galaxy Brain" (HD) Season 15 Episode 12 Sneak Peek

Supernatural 15x12 Sneak Peek "Galaxy Brain" (HD) Season 15 Episode 12 Sneak Peek



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