|Affiliation:||Impossible Mission Force|
|First appearance:||Mission: Impossible III|
|Last appearance:||Mission: Impossible III|
Declan first appears as he takes part in rescuing Agent Lindsey Farris from Owen Davian's captivity in Berlin, Germany, by providing the team with a UH-1 Huey extraction helicopter under his call-sign, Phoenix. Declan is able to pick up all of his colleagues, including Lindsey on board, until her death caused by a micro-explosive detonated inside her head. Ethan reacted to the loss of his protege in tears.
Later, Declan assists in Davian's kidnapping during a charity event in Vatican City and bring him to the United States where the IMF convoy is preparing to transport Davian to the authorities. During the transportation, the IMF convoy is attacked at the Chesapeake Bay Bridge–Tunnel by Davian's operatives and he is able to escape from the IMF's grasp.
After that, the team goes to Shanghai, China and Declan helps Ethan in getting the mysterious dangerous object known only as the Rabbit's Foot. Once the retrieval mission is done, Ethan asks his long time friend Luther Stickell, along with Zhen Lei and Declan, to return home as Ethan has to do this alone. As his team touches down in the airport, they are greeted by the Executive Director of the IMF, Theodore Brassel, and a large group of heavily-armed IMF agents in the tarmac before Brassel says that they seem to have a lot to talk about. Back in the U.S., Luther, Declan and Zhen Lei meet Ethan's wife, Julia Meade, as Ethan has to rescue her from captivity in Shanghai and the couple say farewell as they go for their honeymoon.