Hired Help

Recruit Charon is a minor quest in Fallout 3.

Accepting the Quest
If you speak to Ahzrukhal in The Ninth Circle in the ghoul town of Underworld, he will tell you that he holds the contract of employment (read: slavery) to a ghoul named Charon (also located in The Ninth Circle). Charon is bound to work for whomever holds his contract. Ahzrukhal also tells you that he dislikes having to compete with the other beverage outlet in Underworld, Carol's Place. He proposes that if you were to kill Greta, who works there, he would be willing to give you the contract to Charon.

Killing Greta
Remember that if anyone sees you kill Greta, they will become hostile to you, so the best time to kill her is when she goes on her smoking break just outside of Underworld in the Museum of History lobby area. She appears here around 9:00PM daily. Even if nobody witnesses you kill her, you will still receive Negative Karma.

Also if you have Mister Sandman perk you can easily kill her in sleep without getting any hostility from Underworld's ghouls.

Alternately you can simply buy Charon's contract with enough caps and you won't have to kill Greta.

Another method is to force Greta to attack you - thereby triggering the Underworld Residents to attack her in your defence. This gets you NO negative karma or reactions from other NPCs, you can still raid Greta's body, and the contract will still be yours.

Another way to kill Greta is to use Robotics Expert perk on the Cerberus, the Mr. Gutsy that patrols the Underworld. In the midst of conversation with the robot, those with the Robotic's Expert perk have the option to remove his combat inhibitor. This will cause him to go on a killing spree, attacking any nearby ghouls. It's up to you to make sure that Greta is nearby when you do this. One way is to rely on her smoking break. However, I found another solution. Talk to her when she's in bed. She'll get out of bed and start walking to you to converse. Before she talks to you, back up. Notice that Greta will keep walking towards you. You can now lead her anywhere you want. Now, all you have to do is lead her to the Mr. Gutsy, remove his combat inhibitor, and get the heck out of there. Once he terminates her, feel free to shut him down with a couple pulse grenades. You will receive no blame for her death in this situation, and I don't even think you will suffer a karma loss (not 100% sure on that).

A different way to kill her is by activate a Stealth Boy before entering the hotel. Then simply walk up to Greta, pickpocket her, and move a single frag grenade from your inventory to hers. This will then make the grenade live. Walk quickly out into the corridor and listen for the satisfying bang. Stay hidden until your stealth boy runs out then stroll into The Ninth Circle and tell Ahzrukhal the good news. You'll receive negative karma for this but nobody will suspect a smoothskin of such cunning.

Note: Try not to kill Greta while she is sleeping without the Mr. Sandman perk. Even if you are hidden the others will still become hostile. This is not always true, however. If you have a high enough sneak level and are lucky, you can wake Greta up, sneak behind her, and then attack. So long as you stay hidden for a short period of time (15 seconds?), you will not be marked as a hostile. In addition, you can shoot her with a Silenced 10mm Pistol.

Alternate Way
Charon can also be acquired from Ahzrukhal by paying him either or
 * 2000 caps
 * 1000 caps if you have a barter skill of 50 or higher

Reward
After you murder Greta, return to Ahzrukhal to report your success. He will stick to his word and give you Charon's contract. After you tell Charon that you now have his contract, he will walk over to Ahzrukhal, who will think he's coming to say goodbye. Instead, Charon pulls out his shotgun and blows Ahzrukhals head off.

Bugs
Occasionally, when the player successfully receives Charon's contract and he is en route to 'bid Ahzrukhal adieu', Charon instead simply stands in one spot and cannot be talked to, nor can Ahzrukhal. After this happens, Charon cannot be recruited and both will stand there indefinitely. If you break the law and get the residents of underworld to attack you it will unfreeze Charon and Ahzrukhal. After you make your escape the next time you return to underworld Ahzrukhal will be dead and you can gain Charon as a follower.

I had an error after I killed Greta outside the Underworld during her smoke break. I went back inside, no one attacked. Then I went into Ninth Ring and EVERYONE attacked me at once! I killed them all, looted, and left the bar and no one outside attacked me.

Killing Greta before receicving Ahzrukhai's Request means you will not be able to hire Charon.

Charon will faithfully serve you regardless of your karma. You can have him carry items for you, shoot enemies, use melee attacks, and (surprisingly) use power armor, etc.

Cultural References
Continuing with the Greek Death theme of the Underworld, Charon (pronounced car-on), is the ferryman across the River Styx, which all dead souls must cross in order to get to Hades.