Lieutenant Bert Hall, an ace American flyer serving in World War I as a member of the French Lafayette Escadrille, is wounded in an aerial battle and forced to land behind enemy lines. Finding his German opponent dead, Hall exchanges uniforms with him and is taken to a German hospital to recover. There he meets his old Kentucky sweetheart, who was unable to escape Berlin when the war broke out. Accompanied by the Countess of Moravia, who claims sympathy with the Allied cause but is actually a German spy, they escape to France in a German plane. Through the countess' duplicity, Hall is accused of betraying the French government and sentenced to be shot, but his American lover uncovers evidence that saves him at the last moment.

Helen Merrill sings and dances in the rough Western mining town of Nugget City, where she befriends Myrtle Cadby, whose husband Jake cruelly abuses her. After a particularly vicious beating, Myrtle, seriously injured, shoots Jake. As she lies dying, she gives Helen a letter of introduction to a man she was to have married in the East, urging her to leave Nugget City. Before she leaves, Helen overhears Bill Sheridan and "Snipe" Roach scheming to sell Charles Taylor, a wealthy New Yorker, a salted mine, with the assistance of George Reed, Taylor's mining agent. Helen goes East and learns that Taylor is the man whom Myrtle was to have married, but because she immediately falls in love with him, she conceals her own identity and masquerades as Myrtle.

Ruth Minchin is unhappily married to her father's former business partner, a drunken brute. She contracts a friendship for Severino, a pianist, who lives in the same apartment house, and Minchin, discovering them together, orders the pianist from the room and knocks his wife down. Severino kills Minchin in a delirium following pneumonia, and Ruth is suspected of the crime.