Shanghai

In December 1941, just before the entry of the United States into World War II, an American agent from the Naval Intelligence Office arrives in Shanghai to find his friend Conner was recently murdered. Determined to find out who killed Conner and why, he begins working at The Herald newspaper using the alias Paul Soames, a Nazi sympathiser cover he used while stationed in Berlin. He meets Anthony Lan-Ting, an influential crime lord, and Captain Tanaka (Ken Watanabe) at the German embassy in Shanghai, during an invitation-only event. He later befriends Anthony when he saves him during an attack on Japanese officers by the Chinese Resistance at a nightclub.

Paul realises that Anthony's wife, Anna, organised the attack and is the leader of the resistance. He then decides to help her pass on messages. After finally meeting up with Conner's contact in the Japanese Consulate, Paul finds out that Conner had an affair with a Japanese girl named Sumiko and after searching her home, he uncovers numerous photos, that Conner took, in a darkroom nearby. Some of the photos include Captain Tanaka, other Japanese officers, and the aircraft carrier Kaga.

Unconvinced that Sumiko betrayed Conner, he determines to find her and get answers. After a few more encounters with Anna, Anthony, Captain Tanaka, and investigating an opium house, Paul realises that Sumiko was Captain Tanaka's lover and was seduced by Conner to spy for him. Paul's cover is blown when Conner's contact is arrested, and Paul is interrogated by Captain Tanaka regarding the whereabouts of Sumiko, whose location he does not know. After being released, Anna takes Paul to a safe house where she has been hiding Sumiko, who is on the verge of death due to opium withdrawal and other illnesses.

Anthony gives Captain Tanaka the location of the safe house to save Anna from arrest; inside the safe house, Tanaka informs Paul that the Japanese fleet started attacking Pearl Harbor one hour earlier and that the invasion of Shanghai is also underway. Tanaka admits to killing Conner, but only out of jealousy as he found out about his affair with Sumiko. A distraught Tanaka then asks for Paul's help in administering drugs to ease Sumiko's death. After Sumiko dies, everyone prepares to leave, but Tanaka wants to question Anna which infuriates Anthony, causing him to gun down Tanaka's bodyguards and seriously wound Tanaka himself. Before he can kill Tanaka, Anthony is fatally wounded by a dying bodyguard.

Leaving behind a wounded Tanaka, Paul drives the Lan-Tings away through the burning streets of Shanghai and with his last words, Anthony asks Paul to get Anna out of Shanghai, which he agrees to. Before getting on a ship to leave the city, Paul and Anna encounter Tanaka once again, but Tanaka does not acknowledge them. It is revealed later that both Paul and Anna, at some point, returned to Shanghai.