While the Duchess of Beltravers travels to Bombay, India, jewel thief Gerald Meldrick has a perfect fake made of her famed "Star of Asia" pendant. Gerald then goes to India, posing as a Lloyd's of London detective looking after clients' jewels. Registering at the same hotel is Baroness von Duren, to whom Gerald is immediately attracted. Unknown to Gerald, the baroness is actually Anya von Duren, a thief who also has designs on the pendant.. Gerald soon becomes suspicious of the well-rehearsed Anya, especially when she playfully asks him how someone might steal the pendant. That evening, Anya arranges to dine next to the duchess and, pretending to be a friend of her relatives, Anya accompanies her to her suite. After the inebriated duchess falls asleep, Anya steals the necklace, after which Gerald sneaks into the duchess' room and replaces the real pendant with his fake. He then goes to Anya, takes the pendant from her and convinces her that he is letting her off to rehabilitate her. Anya's gratefulness soon ends when she discovers that he has switched the necklaces, and the next day she confronts him. Gerald suggests that they become partners and they narrowly escape arrest when police Inspector Cressney discovers the theft. Forced to flee on a tramp steamer, they encounter the greedy Captain Chang, who soon receives a wireless offering a £10,000 reward for them. Gerald and Anya soon fall in love, then jump ship together after discovering that Chang plans to turn them in. In Hong Kong, Gerald and Anya are happy, despite their enforced poverty, and Anya dreams of a normal life. Gerald, however, insists that they would hate settling down. One day, Gerald, who was once a British officer, poses as "Captain Huston" in a scheme to confiscate money from a Chinese merchant accused of stealing from the army. Gerald commandeers some unsuspecting soldiers to help him and is so convincing that he is ordered to report to the Hong Kong Garrison for emergency duty. Because the Japanese army is advancing, all Europeans and friendly Chinese must leave nearby Chang-lin, and Gerald is ordered to lead a regiment there. He cannot leave the barracks, but arranges for Anya to meet him at Chang-lin. She is there when he arrives and the evacuation proceeds until Japanese troops march in and refuse to allow any Chinese to leave. Gerald confronts the Japanese colonel, then leads his men and the civilians through their ranks. Additional Japanese forces confront them on the road and a battle ensues. Gerald heroically risks his own life to destroy Japanese machine guns and is seriously wounded before the battle is won. Several weeks later, as Gerald is released from the army hospital, he plans his and Anya's escape, unaware that he is to be awarded the Victoria Cross. Realizing that the army must now know that he is a fake, he wants to leave before the ceremony but cannot get away. After Gerald receives the medal, Inspector Cressney arrives from Bombay to arrest him, and Anya admits that she sent for Cressney after the army uncovered Gerald's subterfuge, but begged them to delay arresting him until after the ceremony. Gerald arranges for some soldiers to arrest Cressney and escapes. Cressney is furious until Gerald returns, admitting that he just wanted to talk with Anya before returning the pendant. He then asks his colonel to keep the medal until he can come back and enlist.