The Crane serum is a powerful hallucinogenic compound which was created by the late Gerald Crane, and utilized by various criminals in Gotham City.


After being paralyzed with terror during the burning of his house (which caused death of his wife), Dr. Gerald Crane became obsessed with overcoming fear, and thus, began harvesting the adrenal glands of people in high-intensity fear situations, killing these victims with their own phobias, in order to maximize their state of terror at the moment of death.[1]

The glands were used in a serum of distilled cortisol that forced the subject to see their greatest fears, in the hope that seeing said fears would allow them to face and overcome said fears. Crane took the serum himself, and became completely fearless as a result of overcoming his fear, ultimately resulting in his death when he initiated a shootout between himself, Harvey Bullock and James Gordon. As shown with Crane's son, Jonathan, a high enough dose of the serum being injected could force the subject to see their fear constantly.[2]

Hugo Strange took to employing the serum in his procedures at Indian Hill, such as using it on Oswald Cobblepot in order to rehabilitate him and change his personality.[3]

The serum is later recreated when Grady Harris and Merton's team forced Jonathan Crane into making a new batch for them to use for crimes. Crane updated the serum's formula and made it into a gaseous version. Jonathan eventually uses the formula himself, upon donning the moniker 'The Scarecrow'.[4] Upon entering Gotham Asylum, Scarecrow gassed Warden Reed and the inmates of Arkham Asylum.[5]


Upon exposure, either through injection or inhalation, the Crane Serum causes its victims to experience hallucinations of their deepest and darkest fears, albeit in a far more demonic and terrorizing form, causing the victims to scream and feel terrorized.


Season 1

Season 2

Season 4

People exposed to the Fear Toxin


Anyone who is exposed to the toxin will see their greatest fear through hallucinations. Eventually the effects will wear off and the victim will revert back to normal, but prolonged exposure can place the victim in a constant state of terror. Victims such as Jonathan Crane and Warden Reed who were exposed for an extended period of time become what they fear. Though as shown with Gordon, people with strong enough willpower can resist the effects, a feat which Jonathan claimed to be impossible to the point that "[one] can't simply stop being afraid, [one] can only become [their] demon".


  • The Crane serum is based off the fear gas that Scarecrow uses in the comics.
    • Interestingly, this version of the Scarecrow's Fear Toxin bears similarities to the "Super Toxin 451-A" from Batman: the Dark Knight (Volume 2).


  1. Stephens, John (writer) & Behring, John (director) (February 2, 2015). "The Fearsome Dr. Crane". Gotham. Season 1. Episode 14. FOX.
  2. Woodruff, Ken (writer) & Copus, Nick (director) (February 9, 2015). "The Scarecrow". Gotham. Season 1. Episode 15. FOX.
  3. Behring, John (writer) & Harper, Jordan (director) (March 14, 2016). "Wrath of the Villains: This Ball of Mud and Meanness". Gotham. Season 2. Episode 14. FOX.
  4. Stephens, John (writer) & Cannon, Danny (director) (September 21, 2017). "A Dark Knight: Pax Penguina". Gotham. Season 4. Episode 1. FOX.
  5. Cannon, Danny (writer) & Milito, Lous Shaw (director) (September 28, 2017). "A Dark Knight: The Fear Reaper". Gotham. Season 4. Episode 2. FOX.

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