A comedy of manners set in the late 1920s, Mirage takes place at the country house party of Gerald and Evadne Fairfax. Newlyweds Pamela and Desmond Borage arrive first, followed by the caddish Dinsdale Morton who swiftly closets himself in the gun room to hide from Pamela, who can't stand the sight of him - or his ukulele. Pamela and Gerald are embroiled in a steamy affair while gin-loving Evadne is hysterical after being disturbed in a state of undress by an "intruder" who turns out to be Desmond. He, meanwhile, is preoccupied with the fact that he has inadvertently signed up for the Foreign Legion. The Fairfaxes' deadpan butler, Butters, oversees proceedings with a cup of whisky-laced tea to fortify himself.