Master thief Blue Jean Billie, the unknown perpetrator of many sensational jewel heists, robs the guests at the exclusive party marking the engagement of Muriel Vanderflip to Algernon P. Smythe, Lord Chesterton. Overpowering Detective Wood, specially stationed there to stop her, Muriel escapes with her chauffeur, Shaver Michael. After Shaver's car overturns, Billie surprises her pursuers, and at gunpoint, makes them return, but Smythe, hiding on the side of Shaver's car, accompanies them until Billie discovers him and makes him take them to his home, where she holds him prisoner. To Shaver's dismay, Billie and Smythe fall in love. After they escape a police raid, Smythe convinces Billie to send the jewels back and marry him. Although she has her doubts when she learns that Smythe is really the international crook "English Harry," after he fights Shaver and locks him and Wood in their retreat with the stolen jewels, Billie and Harry make their final escape vowing to go straight.