Atlee is the overarching antagonist in the 2015 action/thriller film Mission: Impossible - Rogue Nation.
He is a rogue high-ranking MI6 operative and the founder of the mysterious organization known as the Syndicate. After Solomon Lane and the Syndicate went rogue, Atlee tried to hide his involvement in the founding of the Syndicate.
As the supervisor of Ilsa Faust, who infiltrated the Syndicate on his orders, Atlee meets her in London after she has taken the list which supposedly contains the names of the members of the Syndicate. Ilsa realizes that Atlee is about to send her back and tells him, that Lane will not trust her anymore. Atlee states that to ensure her loyalty, Lane will order her to kill Ethan Hunt and tells her to do so. When Ilsa desperately begs him to not send her back to the Syndicate, he threatens to give her up to the CIA. Without a choice, Ilsa takes the stick back and leaves him, returning to the Syndicate.
When with Hunt, Ilsa tells him that the USB drive she gave Lane was empty. Benji tells her that this is impossible and that he is sure that the stick contained the list. Hunt asks her if she had the stick with her the whole time. Thinking of her meeting with her supervisor, she realizes that Atlee must have deleted the files on the stick.
To save Benji, who has been kidnapped by the Syndicate, Hunt and his colleagues have to kidnap the British Prime Minister at an auction. As Chief of the MI6 Atlee is also present at the auction. He is approached by CIA Director Hunley who tells him that the Prime Minister's life is in danger. Atlee then contacts the Prime Minister and leads him to Hunley and Brandt. When Brandt tells the Prime Minister that Hunt is targeting him to take out the Syndicate, the Prime Minister is surprised. He then tells Atlee that he thought that the Syndicate was only an exercise, revealing that he knows about the Syndicate. The Prime Minister then tells Brandt and Hunley about Atlee‘s plans to create a Syndicate of ex-agents which could be used to defeat the British enemies but says that the plans were only hypothetical and that he denied Atlee the permission to do so. The Prime Minister also states that the USB drive does not contain a list of names but accounts containing the budget for the Syndicate. Atlee tries to rescue himself by stating that there is no Syndicate and that Brandt and Hunley have been deceived by Faust, but the Prime Minister stops him and states that Atlee will have to face an investigation. Atlee then shoots the Prime Minister with a tranquilizer and takes off the mask, revealing himself to be actually Ethan Hunt.
The true Atlee then arrives at the building to meet with the Prime Minister. Two guards stop him from entering the room, stating that they have orders to let no one in. When Atlee asks who gave these orders, they answer that he himself did. Atlee and the guards then burst into the room, only to be shot by Hunt with his tranquilizer gun. On the ground, Hunt tells Atlee that they know that he has founded the Syndicate despite his orders and that Lane went rogue. Atlee confirms this.
As Hunt wore a mask that made him look like Atlee, the Prime Minister thinks that Atlee shot him. Atlee was arrested and taken into custody.
Chief Atlee is arguably the Bigger Bad in Rogue Nation and Fallout by virtue of being the founder of The Syndicate. Had he not founded The Syndicate, Solomon Lane would have never gone rogue and the story would not have happened.