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The mysterious serum is a consumable item in Fallout 4.


This consumable is only obtainable through the quests Special Delivery and The Secret of Cabot House.

Eight guaranteed vials can be obtained during The Secret of Cabot House. An additional vial can be obtained if the player character passes a speech check to convince Jack Cabot that no serum was found at Parsons Creamery during Special Delivery, and one more can be gained if the player character sides with Lorenzo Cabot to the very end of The Secret of Cabot House. Should the player character decide to free Lorenzo, they will then gain access to an infinite supply of the serum, with a few caveats. One may only receive one at a time and only when the Sole Survivor has none left, and the serum cannot be sold. Also, one can not hoard the serum in containers, as Lorenzo will know if the Sole Survivor has a vial of it stored somewhere in the Commonwealth.

The item's description lists a Radiation effect of -36000, but this is misleading, as it does not act like a RadAway. Rather, this number comes from removing 10 rads per second for 3600 seconds (60 minutes or one hour).

One potential use for the serum is boosting carrying capacity while scavenging. The boost of +5 Strength is significant, as the similar consumable Buffout only gives +2, and any chem mixed with it +3. Another use is most helpful when the perk Ghoulish is acquired and fully upgraded. When standing in irradiated water without Radiation resistance, the player character will effectively take no new rads, but can gain up to 15 Hit Points per second with the perk. The serum can also be used to heal Andre Michaud in Far Harbor, but Lorenzo will no longer give the player character any more vials if it is used in that way.

Like all other anti-radiation drugs, in Survival mode the serum is affected by Immunodeficiency.


  • One at Parsons Creamery during Special Delivery. The player character can keep it by passing a speech check with Jack Cabot.
  • One in Parsons State Insane Asylum, on the ground next to a raider immediately inside the main entrance.
  • Four in Parsons State Insane Asylum, on the raider Lefty in the room containing Lorenzo's cell.
  • Three in Parsons State Insane Asylum, on a surgical tray on a table in the room containing Lorenzo's cell.
  • Rarely found on raiders in Parsons State Insane Asylum, who must be killed before they use the serum in order to take it from their corpse.
  • One given by Lorenzo if the player character sides with him to the end of The Secret of Cabot House. This can be renewed if the player character has none left in their inventory. See details in the Characteristics section above.


  • The serum is derived from the blood of Lorenzo Cabot, father of Jack Cabot. It halts aging, and in its undiluted form, gives the user incredible strength. It is through this serum that each family member has lived over 400 years. Though the in-game consumable is not addictive for the player character, the Cabot family are psychologically addicted. Emogene, Jack's sister, is the only one who realizes this, as she once went a whole month without a dose but ultimately couldn't stop.
  • It is mentioned by Jack, when talking about the raiders attacking Parsons, that the serum is diluted before the family uses it, and the serum one receives from the raiders and Lorenzo is the undiluted form. Jack explains that while the diluted serum halts aging, the undiluted serum also provides increased strength and damage resistance.
  • It is enormously helpful on the Island, neutralizing the dangers of the fog on the Sole Survivor. The highly irradiated ocean will pull more than 10 rads per second, however.
  • It is enormously helpful while exploring Kiddie Kingdom as well; with its powerful rad remove effect it can almost completely negate the threat of the mist sprayers, especially with a full suit of power armor or a hazmat suit equipped.
  • Both Danse and X6-88 disapprove of giving Emogene the serum in the quest Emogene Takes a Lover (while only X6 takes an approval hit). They state that the Sole Survivor should turn it in to the Brotherhood scribes or the BioScience division, respectively. There is no option to do either.