While in Sooton, the heroes hear that a half-dozen "Gentlemen Caller's" (aka cat-burlars) have died in the past week. The town's underworld is in a turmoil.
A friend of the PCs, on the wrong side of the law, perhaps a Gentleman Caller himself, contacts the PCs to investigate (or, alternately, one of the PCs is a cat-burlar, too, and wants to find out who's doing this).
The PCs spend some time gathering information about the deaths - all seem accidental or at least normal: one drowns in the river (swept away, probably to the falls), another dies in a public knife-fight, a third eats some poison mushrooms, one has a heart attack, the fifth falls in a deep, dry well (still haven't recovered the body, if it will be recovered at all) and the final falls off a building. A rumor going around is that there are another 4 on the list (if the PC is a cat-burlar, he's on it)!
The rumor mill around the town causes the PCs no end of trouble, either casting them as the killers or as working for the underworld. They'll get harassed by both sides of the law.
The first victim (the drowner) is responsible for them all (except no. 5) and is hiding out in town, in disguise. No. 5 saw the writing on the wall and faked his death, too, and is currently outside town, on an old farm. The drowner was cheated by each of the other eight and hatched his revenge.
By the time the PCs get involved and up to speed, victims no. 7 and 8 are dead (sufficated in a privy and beheaded with his own sword). The remaining victim is in hiding - and it's a race to see who will find him first, the killer or the PCs!
Please note: PCs descending into the old, dry well to recover no. 5's body will find a bunch of Morlocks waiting for them!
Killer Gentleman Caller: Thief, Level 3, Alignment: Chaotic; Armor Class: , Hit Dice: 3d6, Hit Points: 18; Attacks: short sword (1d6) + contact poison; Save: T3; morale: 9; Special abilities: thief skills, Ring of Invisibility, Potion of Water-Breathing.
No. 5: Thief, Level 4; Alignment: Neutral; Armor Class: ; Hit Dice: 4d6, Hit Points: 16; Attacks: +1 short sword (1d6+1); Save: T4; morale: 8; Special abilities: thief skills, Hat of Disguise.
No. 9: Thief, Level 1; Alignment: Neutral; Armor Class: ; Hit Dice: 1d6, Hit Points: 4; Attacks: short sword (1d6); Save: T1; morale: 4; Special abilities: thief skills.
Morlocks; No. Encountered: 2d6+3; Alignment: Chaotic; Armor Class: 8; Hit Dice: 1d8, Hit Points: 8, 8, 7, 6, 6, 5, 5, 4, 3, 3, 2, 2, 1, 1, 1; Attacks: short sword (1d6); Save: F1; morale: 9; Special abilities: 90' infravision.