The Amazing Aqua Cura!

 is a Fallout 3 quest that is added to the game in the Broken Steel add-on.

Walkthrough
This quest can be started by hacking Scribe Bigsley's computer in Jefferson Memorial and looking through the logs, a successful Speech check with Bigsley, or by talking to Griffon himself in the Museum of History.

Griffon, a ghoul outside of the Underworld, is selling Aqua Cura (which is basically just Dirty Water), claiming that it will cure just about everything. You learn that he buys Aqua Pura from Bigsley and sells it as Aqua Cura. After getting a bottle from him you can confront him with the fact that your Pip-Boy 3000 detects the water being irradiated; he will deny it and call your claims accusations without proof.

Find Griffon's bottling operation
To find proof, you need to find Griffon's bottling operation. Naturally, the ghoul salesman himself does not want to tell you where it is. However, as he mentioned that Scribe Bigsley's men deliver the Aqua Pura to him, Bigsley likely knows where it is. Arriving at Jefferson Memorial, the scribe will freely tell you that Griffon's operation is in the Museum Authority Building. When you first enter the building go to the very back and find a stair way going downstairs. When you go downstairs take a right into a big room with barrels and tubs. In between 2 tubs on a coffee table are 2 Dirty Water, a Nuka-Cola, a Clipboard, and a holotape. The holotape tells you that Griffon's Ghoul Guards dump the Aqua Pura into the tubs and sinks,selling that to raiders and slavers while he sells unpurified water in aqua cura bottles to ghouls.

Dealing with Griffon
When you go confront Griffon you have three options: blackmailing him; telling him to confess to his audience that his Aqua Cura is irradiated, or you tell them yourself; or telling him you won't expose him so long as he sells real Aqua Pura from that point on.

Blackmailing Griffon
You can blackmail him for 300 caps, or caps every week.

Forcing Griffon to confess
If you force Griffon to confess about the true nature of Aqua Cura, the crowd will turn hostile against him. Griffon will attempt to defend himself, but ultimately runs away and hides in one of the bathrooms at the entrance of the Museum of History. The crowd will follow him into the bathroom where Griffon will make a final stand but is eventually killed by the angry mob. Griffon's body can then be looted for ammo, 400 caps, a Chinese Pistol, Dirty Pre-War Businesswear, and a Wig.

Alternatively, you may kill the four person crowd and Griffon, saying he won't miss them, will run out the front door.

Selling the real Aqua Pura
Although Griffon will tell you to come back in a week, his dialogue will remain the same, simply informing you his business with you is concluded, then trying to pass you off as a happy customer to the crowd. If you kill him the mob will turn hostile and you can loot him for 600 Caps, a wig, a Chinese Pistol, and a Dirty Pre-War Businesswear.

However, if you chose to add the Modified FEV to Project Purity, then The Chop Shop will be full of ghouls suffering from its effects.

Bugs
If you have completed this quest and left Underworld, attempting to return may cause the game to crash. This is very bad if you have entered the Feral Ghoul part of Underworld, as there is no way out except for the Museum Lobby (tested on 360)