"The only thing stopping the hosts from hacking us to pieces is one line of your code."
-Ashley Stubbs, to Elsie Hughes, in "The Stray"
Stubbs is Westworld's Head of Security, under the Quality Assurance Division. He monitors the park to make sure that the Guests are kept safe. He is also responsible for investigating any park disturbances. Stubbs has also been seen having seniority in the control room, having allowed the Man in Black to continue his killing spree. 
Stubbs is waiting with Theresa Cullen when Bernard Lowe arrives, summoned by her, in the Control Room. She tells Stubbs to check on some unscheduled activity in Sub-Level B83, "Cold Storage", and he says he'll take a security detail. Bernard's a little condescending about Stubbs' plans for and armed details and he's a little condescending in return, but there doesn't seem to be any bad feeling between the men. He and Bernard accompany an armed security detail to the sub-level. It's partially flooded. They walk through the level, down the silent escalators and enter the Cold Storage Hall, a large, damp, area full of Hosts, standing quietly in rows. At the back of the hall they find someone in a room, and Bernard stops Ashley when he goes to draw his weapon. He points out that one of the people in the back room is Robert Ford, the Park Director. Ashley hangs back while Bernard goes to speak to him
Stubbs turns up with a team to clean up when Walter starts shooting other hosts earlier than in his script. He goes to look after two guest who were caught up in it while Bernard and Elsie Hughes stay outside. When he comes back out, Theresa tells him to recall all remaining updated hosts and examine them individually.
Stubbs and a Behaviour Tech examine Dolores Abernathy as part of Theresa's recall. When she's brought back online Dolores panics and Stubbs quickly tells the Tech to turn off the effects of her emotions. He calls her "sweetheart", and he's quite gentle with her. While he's questioning her, Dolores tells him that she's terrified - without showing any emotion. He tells her that there's nothing to be frightened of and asks if her father has ever questioned the nature of his reality. Dolores makes excuses for her father, saying that he was scared, not thinking right. He asks her about the picture, she says that it didn't look like anything to her.
Stubbs asks her what it was that her father whispered to her, she says that he told her not to tell anyone. Stubbs reassures her and she reveals that Peter Abernathy whispered "These violent delights have violent ends." in her ear. He asks her if she's ever lied to "us" (the staff at Westworld) she replies no. His last question is would she ever hurt a living thing and she says "No, of course not."
The Tech asks him if he thinks Dolores' core code has been affected? He replies no, that Dolores has been repaired so many times that she looks brand new - but in fact she's the oldest host in the park.
Stubbs is present when a demonstration of the hosts' potential violence towards the guests is given. He tries to restrain Clementine after she kills the other host in the demonstration, but is forced to shoot her when she ignores orders to deactivate and advances on him.
Stubbs debriefs Charlotte and Ford on what happened to Theresa when her body is discovered. He reveals that she was found with a transmitter, and deduces that she was trying to transmit from a high place when she slipped and fell. He listens while Ford and Charlotte speak about matters pertaining to the park's safety and the hosts' narratives, interrupting only to bring up a point relevant to the discussion.
Stubbs is alerted to a signal coming from Elsie Hughes' device, which is somewhere in the middle of the park. He finds it suspicious, as she is supposed to be on leave, and goes into the park to investigate. He finds the area emitting the signal, and suddenly hears a noise. A group of Ghost Nation Hosts appear from the trees, and Stubbs tells them to cease all motor functions. They ignore the command and continue advancing on him. He pulls out his gun and gives the command again, and is about to shoot when he is tackled by a Ghost Nation warrior.
Stubbs is skeptical about the ability of the Delos Incorporated engineers and scientists as he often has to clean up their mess. He is anxious to go into action, in "The Original" he was accused by Bernard of "liking to play dress up more than the guests."
- Season One
- Stubbs' service pistol is a Beretta Px4 Storm Compact. He has stated he carries his pistol with him at all times in the park - even while he sleeps.