Westworld Wiki
Westworld Wiki

They're only yours until they stop working, Bernie. Then they're mine.

–Theresa Cullen to Bernard Lowe about hosts

Theresa Cullen is a main character in the first season and a recurring character in the second season of HBO's Westworld. She was the head of quality assurance at Delos during the events of the first season and is played by Sidse Babett Knudsen.


Theresa is a senior manager, high in the ranks of Delos Incorporated. She is the Head of Quality Assurance and, as such, she is responsible for Westworld's park standards and safety. This includes ensuring that staff, namely Bernard and Ford, are held accountable for their actions.



Theresa Cullen was born in Denmark. As a child, she visited Westworld with her parents. Considering a day in Westworld costs $40,000 per person, her family was presumably very wealthy. She was also known to have at least one sibling: a brother. At some point, she joined Delos and became the Head of Quality Assurance.


Season One

"The Original"

Theresa tells Bernard that one of the Hosts in storage is acting strangely. She warns him that with every update they upload to the Hosts, bugs might surface that could lead to the destruction of Westworld. She says they are overdue for a critical failure since the last happened 30 years ago. After an android malfunction, she insists that Bernard run diagnostics to see what the problem is. Theresa is concerned by the fact that the Hosts can improvise more now with the most recent update. She orders the recall of Hosts who have been updated. To appease the Guests, she makes the saloon heist especially gruesome.


Theresa checks in with Bernard to make sure that all the Hosts are running smoothly. She tells Lee that he is only getting 20 additional hosts to add to his new narrative. Theresa goes to Bernard's apartment and the two proceed to sleep together.

"The Stray"

Theresa warns Bernard about how the board isn't sure about Ford's new narrative. She says that Ford's new storyline is already conflicting with pre-existing narratives. She also asks Bernard why Hosts are still being pulled and if he's keeping any problems from her.

"Dissonance Theory"

Theresa's team takes over the investigation of the wandering Host. Theresa meets with Ford at a restaurant in Westworld that she visited as a kid. She informs him that a board representative will be arriving soon to see the new narrative. Ford warns Theresa to be careful with Bernard, confirming that he knows that they are sleeping together.

"The Adversary"

Theresa tells Bernard that Ford knows about their relationship. She breaks up with him as a precautionary measure. She visits a drunken Lee at the Mesa bar and asks him to come back to work. He refuses, so she leaves, but not before telling him to sober up. Bernard shows up at Theresa's apartment to talk about the anomalies in the park. But before he can, Elsie calls and warns him that Theresa is the person responsible for the information leak.

"Trompe L'Oeil"

Theresa, along with Charlotte Hale, devises a plan to prove Ford's edits to the Hosts are making them dangerous. They do so by resetting Clementine Pennyfeather and thus shorting out her key response functions. Hale fires Bernard after showing the effects to the board and seeds doubt as to whether Ford can be of any more use to the company. Bernard, worried about Elsie, confronts Theresa about both the hidden house and them sneaking information from the Hosts. Theresa explains that they only were doing so in the case that Ford would wipe out the Hosts' memories upon his "retirement" from the company. Bernard leads Theresa to the house where Ford's host family live. They find a hidden lab in the basement with blueprints for both Dolores and Bernard himself. Bernard is visibly shaken to think he has been a host this whole time. Dr. Ford walks in. Theresa realizes that she is trapped with those who wish to keep Ford's creations a secret, and attempts to signal for help; her phone is unable to locate a signal, however. Ford orders Bernard to kill Theresa and then clean up and destroy any evidence. Bernard politely takes off his jacket and tie and places them neatly on a chair. He attacks Theresa and kills her. Bernard then quietly puts his jacket and tie back on and goes with Ford. 

"Trace Decay"

Theresa's body is unveiled in one of the rooms of the Mesa Hub, with Charlotte, Ford and Stubbs present. They discuss the events of her death.


Killed By

After learning that Theresa is aware of Ford's plans, Robert orders Bernard to kill Theresa to leave no witnesses. Bernard obeys and smashes her head to death.

Related Casualties

This list shows the victims Theresa has killed:


Theresa is very smart and calculating. She was clever enough to plan ahead in the event of Ford leaving and wiping the Hosts' memories, and also had the foresight to end her relationship with Bernard as a precaution after Ford found out. She also hatched a plan with Charlotte to get the board to oust Ford.

She doesn't appear to have a stomach for violence, as in Trompe L'Oeil she hastily ended the part of the demonstration where Clementine Pennyfeather was beaten by a male Host, turning away from the sight.


Bernard Lowe

Theresa was in a clandestine relationship with Bernard Lowe, however, she broke it off after Ford found out about it. She appeared to trust him completely, as shown by when she willingly followed him into an unknown section of the park - despite him having just revealed that he knew she was transmitting information outside the park.

Lee Sizemore

Theresa doesn't appear to like Lee Sizemore.



  • Lisa Joy and Jonathan Nolan were both on set for Theresa's death scene.[1]
  • Despite having an English-sounding name, Theresa is confirmed to be Danish by Lee Sizemore during his drunken rant.


The gallery below is automatically generated and contains images in the category "Images of Theresa Cullen". Images added to that category turn up in the gallery after a short time, but you can also add images using the Add button.