Colin Moriarty

Colin Moriarty is Megaton's crime boss and the owner of Moriarty's Saloon, and speaks with a slight Irish accent. The last name Moriarty is Gaelic, presumably he's a Gaelic descendant. He seems to be the only Irishman in the Capital Wasteland, except, perhaps, Reilly.

Biography
Colin Moriarty was born in 2227 and has lived in Megaton almost his entire life. Moriarty's father came to the former United States from Ireland with his young son, and amassed his wealth using the nearby trade routes, which helped secure Megaton as a trading hub in the area. Colin's father died during a raider attack in 2241 and his son inherited his wealth, including the saloon.

Following in His Footsteps
Moriarty has a computer which contains valuable information on the game's main quest. To access the information, you can either pay/speech Moriarty for it, get the info from Nova, the local prostitute working for Moriarty, or convince Gob, the ghoul bartender, to tell you how to access his boss' computer. The player can also go into sneak mode, pickpocket Moriarty's key from him, use it to open a cabinet in the back that contains his computer's password and gain the information that way. If you pay Jericho 20 caps for information, he will tell you that Moriarty keeps the payroll for Nova and Gob locked by his bed. Moriarty's bed is located upstairs in his saloon. Jericho informs you that Moriarty keeps the key around his neck.

If you are planning on blowing up Megaton and thus are not worried about bad Karma and can catch Moriarty in the back room at his computer, you can close the door and kill him (after talking to him about your father) and loot him and everything back there.

300 Pieces of Silver
If you tell Moriarty you don't have 100 caps to buy information on your father, he will give you a cap raising task. He wants you to find a woman called Silver and get his money back. You can find Silver north-west of Megaton at Springvale, inside a ranch house.

You can keep all 400 caps Silver drops, assuming you didn't tell Moriarty that Silver is gone, if you acquire the information an alternative way; otherwise, she drops only 100 caps (which you can still keep).

Appearances
Moriarty appears only in Fallout 3.

Known bugs and solutions
Moriarty has been reported to disappear into the wasteland making it difficult to complete the main quest. To determine if this has happened, select a quest involving Moriarty as the target (generally Following in His Footsteps), then bring up the World Map. If the marker for Moriarty appears north-east of Springvale School, then you can safely assume he has wandered away. Alternate solutions for this phase of the quest line involve stealing or hacking Moriarty's computer, resulting in Bad Karma. This small amount of negative Karma can easily be mitigated by other good deeds throughout the wasteland. Also, the player can simply skip this phase of Following in His Footsteps by mentioning to either of next two contacts in the quest line that you are looking for your father.

After vanishing from Megaton, Moriarty can sometimes be found standing in the blank void outside of the city's walls. Players can only access this area through the console, or by climbing on top of Lucas Simms' house and jumping over the outer walls of the city. How the Moriarty NPC winds up here is unknown; it may be a spawning problem. If found, he can be spoken with normally and can even trade items. After using this method to finish any required business with the character, players can return to the map by fast traveling via their Pip-Boy.

While playing PC version you can also bring him back by following Recovering missing NPC in Fallout 3 guide.

Using the Mesmetron on him will have the same effect on all non aggressive npcs. However even though he dies, the other npcs in the town will all act as if he is alive and you will still get the objective to talk to him about Dad.

If he is killed, Gob does not change his dialog, and Manya does mention Lucas being dead.