Muriel Walker is a minor antagonist of White House Down. She is the widow of Martin Walker, the corrupted head of Presidential Detail.
She was portrayed by Barbara Williams.
Muriel is first seen when her husband is seen getting ready for work on the fateful day the White House is taken over by terrorists. He is seen loading his Beretta 92FS pistol and removing his American flag pin and placing it next to a picture of their late son, Kevin. It is later revealed that Martin himself is working with the terrorists, who are just mercenaries led by Emil Stenz, to hold President James Sawyer hostage and destroy his peace treaty in revenge for Kevin's death. Muriel is later brought in by Special Agent Carol Finnerty and initially, she agrees to talk down Martin and beg him to just come home. After hearing her husband's justification, rather than telling him to stop his rampage, Muriel instead tells him to continue on and avenge the death of their son, much to the horror of Carol. As a result, Carol arrests Muriel and places her under federal custody, blackmailing Martin to call off the attack on the White House or else his wife will never be released out of prison. Martin didn't care, and continued the attack anyways.
Following the deaths of her husband and the mercenaries, Muriel was sentenced to life in a federal prison as Carol promised.