Holy Water (quest)

Holy Water is a Fallout 3 quest that is added to the game in the Broken Steel downloadable content pack.

Walkthrough
NOTE: You cannot do this quest if Megaton was destroyed during The Power of the Atom quest!
 * 1) You pick up this quest from Scribe Bigsley after asking him what you can do to help. He asks you to investigate the area around Megaton to see why they need more water, after just being sent a week's shipment of Aqua Pura.
 * 2) After arriving at Megaton, you will witness a 'cutscene' of sorts. An NPC named Rosa will give a water beggar, a bottle of seemingly pure water. He drinks the water, and dies.
 * 3) Rosa then approaches you, and after a short conversation she reveals that she received the water from a church in Springvale. The Church is marked on your map.
 * 4) After finding the Church, you will find Brother Gerard. He will give you some Holy Water (item) and will not speak to you until you have drunk it. He will reveal that the leader of the church, Mother Curie III, has been blessing water so that wastelanders may "bask in Atom's Glow". You may ask Gerard if you can meet Mother Curie III but you must either be irradiated, pass a speech check, or pick the lock (Very Hard). Alternatively you can kill Gerard and loot the key from his corpse.
 * 5) After either becoming irradiated or passing the speech challenge, you enter the basement of the church by means of a trap door. Mother Curie is giving a sermon to two ghouls as you enter. Once she finishes the sermon she engages you in conversation. She tells you that she has been intercepting the Aqua Pura from the Brotherhood caravans (who she sees as "angels") and turning it into holy water. She does this because she wants to share Atom's gift with the people of the Capital Wasteland. This gift is ghoulification.
 * 6) From here on out, you have three options. You can talk her out of stealing water with a speech challenge or Charisma check, you can murder them all or you can irradiate yourself to an extremely critical level. If you do, Curie will think you're the Prophet of Atom and will willingly give up irradiating the water as if you passed a speech or charisma check. You can irradiate yourself in the basement and next to the bath tub on the floor level using a radiation trap that is turned on with a switch on a pillar next to the generator(basement) on the podium (wasteland level). Be wary if you decide to kill them, as downstairs in the next room, there is a Feral Ghoul Reaver (named "Atom's Champion") and a Glowing One, both of which will turn hostile.

Megaton Alternatives
See point 2 & 3. You can find a note pinned to the door of your Megaton House, that leads you to the church. Alternatively you can speak to an NPC sitting next to the Brahmin at the bottom of the hill where you enter and he will give you the Holy Water Pamphlet. A NPC will so come up to you and complain about a cult stealing Megaton's water.