Adventures (D&D 4E) Ideas for Waterdhavian slavers

[offby1]

I'm going to be writing a late-heroic-tier adventure -- probably a bridge between heroic and paragon, to be honest -- adventure in Waterdeep. I'm trying to work it around three backstory elements:

1. One party member is an extraplanar foundling with no memory of his past. The player has provided enough backstory to give me total freedom in how or even if this affects play.

2. One party member has a family business in Waterdeep that will, hopefully, provide the hook to travel there.

3. One party member is a Gnome who used to be a slave of the Fomorians in the Faewild.

I'd like to put together something that ties these three aspects of the party together, basically with the party -- already well-established heroes of level 6-7 -- traveling to Waterdeep to assist party member #2's family with something that turns out to be a lot bigger. Basically, beating up thugs in the alleyways isn't going to be too exciting at this level.

I'm open to any and all suggestions, because although I have this very, very vague outline in mind, I really don't have a lot else.

It's worth noting that I have a few months to get this ready, so I'm not asking for stuff that'll work tomorrow. I want to be well prepared.

[weem]

Maybe #3, after escaping (or being rescued) encountered a wandering #1 while heading to a nearby town. #1 seemed to need help and was lost, so they traveled together.

Once in town, perhaps they overhear someone talking about how their cousin went to Waterdeep and was making decent money working for X business (#2's family business) and that they were looking for more people... the person they overheard was considering heading there himself.

The gnome, pretty much starting fresh, is broke and it's the first real option he has heard of to get back on his feet... the amnesia'd one could be drawn to that as well, or perhaps has found a friend in this gnome by now and decides to go along, more to hang with him than work. Maybe he feels the huge city might have a clue about who he is.

[offby1]

I should be clear; by the time this sets up, the whole party will have been together from levels 1-6+. There's no need to introduce them, there's just a need for a tailored adventure.

[Stoat]

The Fomorians are in league with an extraplanar menace (I like devils) who run a slaving ring. The slavers kidnap someone close to Player #2.

[offby1]

Okay, I like that. That's got some potential. Devils... how would they operate within the walls of Waterdeep? Would there be Fomorians, or proxies? My Realms-fu is weak, and I don't imagine there's a Waterdeep sourcebook kicking around anywhere since 4E came out, right?