A3-21, also known as Harkness, is an android and Rivet City's security chief in the year 2277. His past is scattered across the Capital Wasteland for the Lone Wanderer to find and decide what fate will befall him.
Rivet City's hard-nosed security chief, 35-year-old Harkness is a good guy and a good friend, despite his demeanor. What he doesn't know is that he isn't even human; he's a sentient humanoid robot who escaped from his creators, had facial reconstructive surgery and a mind wipe. Harkness is extremely fair-minded. He treats Hangar Deck citizens with the same regard as Upper Deck citizens. As a result, he is very well liked by the Hanger Deck residents.
Harkness is a synthetic humanoid, or "Synth", and is the most advanced android ever created by The Institute, as of 2277. He worked for the Synth Retention Bureau in the Commonwealth, before attempting to escape after sympathizing with the escaped synths he was tasked to capture. The synths working at the Synth Retention Bureau are told that those who try to escape are simply malfunctioning, when in actuality their complex AI has allowed them to start thinking for themselves. The synths that Harkness captured filled his head with ideas about self-determination and freedom, contributing to his decision to escape. “Self determination is NOT a malfunction,” as Harkness would later say in a holotape before escaping.
He successfully escaped the Commonwealth but was hunted by the Synth Retention Bureau, and had to get surgery to get a new face and voice, as well as having his memory erased, in order to thwart the Bureau and start a new life. After some searching he found Horace Pinkerton, a skilled surgeon who agreed to perform the facial construction surgery and memory swap. After this, he got a job at Rivet City as the security chief.
During the day, Harkness will be outside Flak 'N Shrapnel's weapon store in the Rivet City marketplace. He may be on the top floor of the Bridge Tower from midnight to 6:00 a.m. When meeting him for the first time, if the player tells him you are going to leave, he'll be stuck at the entrance for the rest of the game. However, the player can still walk past him without incident.
The Replicated Man: Harkness turns out to be the android which Dr. Zimmer is looking for. The Lone Wanderer can make a choice to either help Harkness or Zimmer, who then takes him back to the Commonwealth.
If the player does not return Harkness to Zimmer, Harkness will stay in Rivet City in a loop, unable to die. If one waits to activate his recall code he will give you his plasma rifle, after which the player can still turn him in and gain a reward from Zimmer.
During The Replicated Man quest, after Harkness finds out he is an android and the player is following him downstairs to the science lab, he can be pickpocketed for the key to the Ship's Armory.
If the Lone Wanderer allows Zimmer to reclaim Harkness, Zimmer will use a command to restore Harkness to his factory settings.
If the player has the Contract Killer perk and kills him through the Console Commands, he'll have 4 ears instead of one.