The 39 Clues Wiki
The 39 Clues Wiki

The Serum Antidote was the main focus of the Unstoppable arc. The Serum Antidote was made by Olivia Cahill. She learned how to make the antidote from her time as Leonardo Da Vinci's apprentice. Apparently, the Serum Antidote only affects those who have taken the Master Serum directly, not those who have inherited the traits granted by the Master Serum and the Ingredient Serums from their ancestors. It was made by Sammy Mourad in Flashpoint, when the Cahills were assembling the antidote to save Amy's life. Four of the ingredients were found by Amy and Dan during their travels in an attempt to stop Pierce while three of them were found by various other Cahill agents (a reference to the online games played on

Antidote Locations/Ingredients[]

Troy : Six whiskers from an Anatolian leopard, ground to a powder. Amy and Dan found this in Nowhere to Run.

Carthage: Silphium, tincture one dram. This is found in Breakaway.

Tikal: Riven crystal, one dram ground to a powder. This is found in Countdown.

Angkor: Venom of a Tonlé Sap Water Snake, half jigger. This was found by Cara Pierce in Flashpoint, and given to Amy, Dan and the others by her.

Pueblo : One head of an ancient piece of corn. This ingredient is found in Unstoppable Mission 1: Written in Stone.

Britannia: Copper butterfly wings. This ingredient is obtained from Unstoppable Mission 2: The Queen's Wings.

Abyssina: Boiled roots of three dingetenga plants. This ingredient is found in Unstoppable Mission 3: Royal Roots.