Grouse was born in 2247, and he has been with the slavers since he was a teenager (he is now 30). His father was the former leader before Eulogy usurped him and rose to power, and Grouse has a legacy to live up to. He isn't fond of Eulogy, but he knows that if he moves against him, most of the slavers would turn on him. He sits at the checkpoint entrance wearing a permanent scowl.
Strictly Business: Grouse mentions that Eulogy Jones wants to acquire some VIP targets. If you accept his proposal to capture some slaves he will give you a list of four targets. He will allow you to enter Paradise Falls after the first capture.
Strictly Profitable is an unmarked quest that can be pursued simultaneously to the Strictly Business quest as well as after that quest's completion. You can enslave certain people (with a Karma hit) and Grouse will pay you 250 caps per slave and give you a new collar for the next victim.
Grouse is the only source of slave collars in the game. Should Grouse die the player will be unable to obtain a new slave collar or caps for a successful enslavement. However, so long as the player has a slave collar in inventory they will be able to use it to enslave a mezzed non-player character, albeit for no reward other than negative Karma (and removing the enslaved non-player character from the game).
He will become hostile if the player preaches to him for the second time after he dismisses the player. This will cause the rest of the slavers in Paradise Falls to become hostile as well.
"I'm glad you asked! I got this Mesmetron thing. It's some kind of stun gun. I want you to test it out for me. A little research project. You take this Mezzer. Shoot it at some poor schmuck. While he's in la-la-land, you slip one of these collars over his head. Be careful with that collar. It'll explode if you tinker with it. Tell the slave to boot it over here pronto, or his head'll pop. You got all that? I hate repeating myself. That Mesmetron came with some kind of manual. I don't have time for that bullshit, so you better know how to read."
"Are you kidding me? You've never heard of Paradise Falls? Oh, right. The suit. You're right out of the vault, aren't you? Great. Shit, you're lucky you're not up there in the pens, dumbass. I can't believe you. Anyway, Paradise Falls is home to the Slavers. Up there, we sell the slaves that we capture out in the Wastes. So, unless you're either buying or selling, piss off."