In the Belly of the Beast (Penumbra (D20))

It is a cancer thriving in the midst of a bustling city, a shadowy conspiracy bent on driving House Mezzia, a once proud and noble merchant family, to its knees. Forced to turn to outsiders for aid, a young scion of the Mezzia clan needs heroes to stand with him against encroaching darkness - heroes who are willing to follow him through the dark heart of the underworld. A fantasy adventure in the top-selling Penumbra line for the D20 System!