Cure Jarvis of Radscorpion Poison

When you first enter Shady Sands and talk to Seth, ask him about the Radscorpions. He'll tell you about his brother Jarvis who has been poisoned and that you should speak to Aradesh for more information. This will activate the Stop the Radscorpions quest. You'll then be provided with a dialog option with Seth to be taken to the Radscorpion caves. Don't do this just yet.

Go talk to Aradesh, and ask him about what's going on in Shady Sands. He'll mention the Radscorpion attacks on their Brahmin herd and tell you to talk to Razlo, the doctor.

Go talk to Razlo, and ask him what he knows about Radscorpions. Follow the dialog for more information to get the information about collecting the stinger in the tail.

Go back to Seth, and have him take you to the Radscorpion caves. He will not join you in taking them out, but you can optionally get Ian as an NPC before you go. When you've killed the Radscorpions, search the corpse to collect the tail. They're heavy, so factor that into your inventory.

When you leave the cave, you'll be taken back to the map of Shady Sands. Go talk to Razlo and tell him you have a sample of the poison. He'll make an antidote and give you a free sample. You get 250 experience points for helping create the antidote. Use the antidote you receive from Razlo on Jarvis. You will receive 400 experience points for your trouble. You can have Razlo make more antidote for you for free from additional scorpion tails, which then can be used when poisoned or bartered.

Note that you can also just cruise around outside of Shady Sands until you run into a Radscorpion random encounter, but that may take a while.