Cure Jarvis of Radscorpion Poison

Cure Jarvis of Radscorpion Poison is an unmarked quest in Fallout.

Detailed walkthrough
The Vault Dweller must first speak to Seth, who says that Jarvis, his brother, has been poisoned and that they can speak to Razlo for more information. Razlo is located in the building to the south. He will then tell the Vault Dweller that he can create an antidote to the venom, but he requires the venom sack from a radscorpion, which is inside their tail.

Once the Vault Dweller has obtained a radscorpion's tail, bring it back to Razlo, who will create an antidote and give the Vault Dweller a free sample for personal use.

Only then can the Vault Dweller open the curtain to the back of Razlo's hut where Jarvis is laying on a mattress. Using the antidote on Jarvis finishes the quest.

Regardless of the Vault Dweller's Intelligence, they can still use antidote on Jarvis after obtaining it. A Vault Dweller with an Intelligence below 4 will not be able to learn about this quest from Seth. Instead, visit Jarvis in the back of Razlo's hut and try to talk to him. He will then give some floating dialogue telling the Vault Dweller about his ailment, and that they should see Seth if they want to help remove the radscorpion threat.

Locations of scorpion tails

 * Scorpion tails are dropped by all radscorpions on death. However, they are quite heavy, weighing 20 pounds per piece.
 * If the Vault Dweller speaks to Aradesh and agrees to help his people by destroying the radscorpions, they will begin the quest Stop the Radscorpions. Part of the quest involves eliminating radscorpions inside their caves. There are a total of nine radscorpions inside the caves.
 * Radscorpions can spawn around the entrance to Vault 15 the first time the player character visits if they failed a Luck check.
 * Radscorpions may be randomly encountered anywhere on the world map.

Rewards

 * 400 XP
 * +1 Reputation