A Manhandled Manservant

 is an unmarked Fallout 3 quest.

Receiving and completing the quest
Argyle has not been seen since he was separated from Herbert "Daring" Dashwood on their escape from Rockopolis. The retired adventurer refuses to believe his manservant died in that battle though, instead believing he is still out there somewhere. Upon visiting Rockopolis and finding Argyle's corpse, the player may return the news to Herbert Dashwood at Tenpenny Tower for a reward.

Dashwood, sad to hear of Argyle's demise (he always thought Argyle would outlast him by at least 100 years), tells the player that his days of adventuring are over and gives the player the key to his safe.

Rewards
Inside the safe are Bottle caps, Mentats, a Mini-Nuke, Rad-X, Schematics - Bottlecap Mine, a Stealth Boy and Stimpaks.

Taking the Bottle caps will result in negative karma and he will become hostile. If you leave the bottle caps, he will not become hostile.

Bugs

 * You can take all the caps in the safe and Dashwood will not become hostile, provided he has given you the key. (Confirmed on Xbox 360 and PS3)