The Thieves' Guild is a group of thieves in the Hub's Oldtown led by the slightly crazed Loxley. Their main hideout can be found in the basement of a junkie's home. The guild is loosely based on the 'old stories' as Loxley calls them of Robin Hood and his band of merry men.
Members
The leader of the guild is Loxley who has his own room and three guards in the hideout. The three guards include Jasmine, Cleo and Smitty. Jasmine is Loxley's assistant who handles all the details of assignments and payment. Cleo is the only member who doesn't seem too reluctant to communicate with you. She will give you a great deal of information on the Guild and how they feel about the rest of the Hub. Smitty doesn't have much to say, he actually seems pissed out off about you even being alive.
The only other members of the Thieves' Guild ever mentioned are the four guards in a different building in Oldtown closer to the entrance. They are guarding an initiate from the Brotherhood of Steel they have captured, but remain unnamed.
Quests
The guild, if the player is accepting, possesses a quest to steal a diamond necklace from Daren Hightower in the Heights. If successful, the Vault Dweller is rewarded with an Electronic Lock Pick, which is very useful for breaking into the Mariposa Military Base, and some bottle caps. Jasmine tells you not to kill Mr. Hightower, but if he is killed you will be rewarded just the same.
Talus from the Brotherhood of Steel at Lost Hills can trigger the Rescue Initiate from the Hub quest, or you can take care of the quest before you run into him. The initiate is in a building in Oldtown with four Thieves' Guild guards.
Sources
Dialogue Files: Loxley, Jasmine, Cleo and Talus Template:Hub Factions