|“||We all have to make sacrifices for our country.||„|
|~ Walker to President Sawyer|
|“||You think I would put my country through this for MONEY?!! I hate mercenaries!||„|
|~ Walker after killing one of his mercenaries.|
Martin James Walker is the hidden secondary antagonist of the 2013 film White House Down. He is the corrupted head of Presidential Detail and works for Eli Raphelson (the true main antagonist).
It is known that Martin Walker had political ambitions before the film's events, since he is the head of Presidential Detail. His son Kevin was a soldier in the US Marine Corps, but one day Kevin was killed in a mission in Iran, and therefore Martin (and also his wife Muriel, who is Kevin's mother) fell into depression and anger over Kevin's death. Martin pressed for military action against Iran as vengeance, but because President James Sawyer enforced peace with Iran, Martin became outraged and therefore he put the film's plot, an assault on the White House, into action in order to fulfill his revenge at the Iranians for killing Kevin.
A man disguised as a janitor sets off a bomb at the center of the US Capitol building. White House Speaker Eli Raphelson, who was in the Capitol, remains unharmed and is taken to an underground command center with Finnerty, while Vice President of the United States Alvin Hammond (Michael Murphy) is taken aboard Air Force One. The White House is put on lockdown, separating Cale from Emily, who had left the tour group to use the restroom. Meanwhile, mercenaries led by Emil Stenz, who had disguised themselves as video technicians to get inside the White House, start killing off all security officers and take the tour group hostage, but Cale manages to take a gun and escape to go find his daughter. Walker escorts the President and his detail to the Presidential Emergency Operations Center. Once Sawyer gains access, Walker kills his detail, revealing himself to be the real leader and wants vengeance against Sawyer after a botched black ops mission resulted in the death of Walker's son. Cale, who failed to find Emily, kills a mercenary and takes his gun and radio. Overhearing the radio, Cale locates and rescues Sawyer. The authorities then decide to bring in Walker's wife Muriel to talk some sense into her husband. At first she agrees and pleads him to stop and just come home but after hearing him justify it she instead convinces him to carry on with the plan to avenge their son's death, which resulted Muriel to be placed in a federal prison for life.
Walker and Stenz bring in their computer specialist Skip Tyler to hack into their defense system, but they still require Sawyer to activate the nuclear football. They locate the remaining chain of command and execute the Secretary of Defense before putting them with the hostages. Emily, while hiding, records a video of the mercenaries and puts in on YouTube before eventually being captured. Cale and Sawyer manage to reach out to the command structure through a satellite phone Sawyer keeps to communicate with his wife and they tell Cale to get the President out through underground tunnels. At the command center, Finnerty uses Emily's video to discover the mercenaries' identities, who used to work for various government agencies. They also discover that Walker has an inoperable tumor, suggesting his involvement to be a suicide mission and that the attack is meant for more dangerous reasons. Cale and Sawyer find the tunnel gate rigged with an explosive and are forced to escape with a presidential limo. After giving chase with Stenz on the White House lawn, Cale and Sawyer get flipped into the White House pool after Cale gets distracted by a mercenary holding Emily at gunpoint. A gunfight erupts which results in an explosion that leaves Sawyer and Cale presumed dead. Hammond is then sworn in as acting President.
When Cale and Sawyer reveal they are still alive, they learn Hammond has ordered an aerial incursion to take back the White House. Knowing the mercenaries have Javelins, Cale tries but fails to stop them from shooting down the choppers. Cale gets into a fight with Stenz and ends up dropping his White House passes for himself and Emily while escaping. Having already learned of Emily from the video, Stenz, now knowing she is Cale's daughter, takes her to Walker in the Oval Office. Meanwhile, Tyler finally finishes the upload into NORAD and launches a missile at Air Force One, killing Hammond and everyone on board. Raphelson is then sworn in as acting President and reluctantly orders an air strike on the White House, which Cale is informed of.
Walker tells Cale over the White House intercom to surrender Sawyer or he will kill Emily. Sawyer ultimately surrenders himself to save Emily. However, he refuses to activate the football. When Walker threatens to kill Emily again, the alarms and sprinklers are set off by Cale setting various rooms on fire. Tyler is killed trying to escape by the bomb on the tunnel gate having been tampered with so it goes off rather than disarm when he leaves. After killing most of the remaining mercenaries and freeing the hostages, Cale is confronted by Stenz, who is ultimately killed by a grenade belt. Sawyer attacks a distracted Walker, who ultimately gains the upper hand and uses him to activate the football before supposedly shooting him dead. Using updated launch codes received by an anonymous source, Walker targets various cities in the Middle East, but before he can initiate the launch, Cale crashes into the office in a Presidential escort vehicle. Despite being pinned to the wall by the vehicle, Walker still attempts to press the launch button but Cale finally kills him with a mini-gun before he gets the chance.
Following the deaths of Walker and other mercenaries, it is later revealed that Raphelson was the one who hired Stenz and his mercenaries to help Walker formulate the attack on the White House, since Raphelson actually disagreed on President Sawyer's peace treaty and plots to have Sawyer murdered during the attack, as well as Vice President Hammond, so that he can be the new president and destroy the peace treaty. Cale also learned that Walker received the launch codes on his pager from Raphelson, so he used the pager to dial the call-back number, exposing Raphelson as the true mastermind behind the attack. When this was revealed to everyone, Raphelson gets arrested to face trial from his crimes.