His past is not known but he is known to the public as an important government official and the Director of FEMA. He was appointed to FEMA through Page's manipulation of an unnamed senator infected with the Gray Death, and went to work immediately. A cloak-and-dagger man, Simons was the first higher-up on the scene after JC Denton's capture of NSF operatives in Battery Park; his interrogation ended with Simons personally executing both prisoners.
As one of the few nano-augmented humans at the time with Bob Page, JC Denton and his brother Paul, Simons is widely considered one of the most dangerous men in Majestic 12. He has no sense of humor and only tolerates others as long as he needs to. Although augmented with numerous combat-aiding modifications (his face is marked-up with bioelectronics), he claims that they are strictly for increased ability for work in FEMA disaster relief. His nano-augmentations make him immune to gas, flames, plasma ammunition, and prods. He's also very resistant to small arms ammunition, and he possesses a targeting aug and a remote explosive detonation aug. He also travels with an escort of two or more Men in Black. Simons' nano-augmentations are mostly combat-oriented, and it is revealed later in the game that he carries a plasma rifle, a LAM Grenade, and a Dragon's Tooth Sword – the Plasma Rifle and Dragon's Tooth Sword are high-powered weapons with almost instantly lethal capabilities.
As well as being a skilled fighter, Simons is also a Machiavellian politician, who uses his skills in intimidation to coerce and command his numerous underlings. This can be seen during his conversations with UNATCO head Joseph Manderley, a bureaucrat who Simons has put in such a position of power due to his willingness to be ordered by MJ12. Late in the game, Simons hunts down JC in one of MJ12's offshore bases with the intention of killing him. If he fails here, he last shows up in the command building at Area 51, again after JC.
Simons has a tendency to continually charge his bioelectric reserves, keeping them at 100% efficiency. This causes an intermittent sharp pain behind his eyes, advised by Jaime Reyes to quit that habit. He is responsible for Joseph Manderley's death if JC Denton doesn't kill him when he escapes from UNATCO HQ. In an interrogation, he kills two NSF soldiers who don't cooperate, even though he says he has information about their families.
"One must admire a man who can keep a secret, because he has value."
"I am a patient man... But not that patient."
"You will confess, by the way. I don't like to dirty my hands with that sort of thing, but you will confess."
"The real plague, eating at the minds of the American people, is secessionism, regionalism, this new arrogance and sense of entitlement."
"Once the bug bites, you've already lost the patient."
"Do you even have a passing interest in doing your job?"
"Am I behind a desk right now? No, I'm not."
"Denton? Walton Simons here. What an expensive mistake you turned out to be. I ordered the troops to kill you, because frankly I don't have the patience to wait for one of those damn killswitches to work."
"You can't run, Denton. Even if you escape, your killswitch is counting down. You'll be dead in twenty-three hours. Another fifty billion dollars down the drain."
"We did certainly teach you how to fight, didn't we?"