There's been trouble brewing in the city lately. A foul smell has begun creeping up through the storm drains and the water in homes and businesses has grown rank and sickening. The Council of Nine, the ruling body of the city, have put out notice of a reward for anyone who can purify the city's water source and deal with the horrible stench. The worst of things seems to be centered around a particularly wealthy part of town. Some believe that something in the sewers is causing this. Perhaps an otyugh or some other manner of filth creature. At least one adventurer has gone into the smelly depths, but he hasn't yet returned. Maybe you'll have better luck?
Check out this awesome D&D 5e adventure for a party of four 1st level heroes!
UPDATE: Updated the PDF with a more modern look and made some minor balance tweaks.