In March 2006, Frost was among the experts in extraterrestrial events gathered by the British government following the destruction of Big Ben by a crashing alien spaceship. Accompanied by two other UNIT officers drawn from the US Army, she attended a meeting held by acting Prime Minister Joseph Green and General Asquith at 10 Downing Street. She was killed along with the other experts when Green, revealed to be an alien in disguise, used a remote control to activate devices planted in their ID cards to electrocute them. (DW: "Aliens of London", "World War Three")
Muriel Frost was played by an unknown performer.
Frost's uniform displayed numerous military awards, including the Army Presidential Unit Citation and the Army Meritorious Unit Commendation. She was also a recipient of the Combat Infantryman Badge. The uniform has a United Nations patch and four service stripes, indicating twelve years of service.