The story of spies working for different countries attempting to decode coded weather forecasts.

The story of spies working for different countries attempting to decode coded weather forecasts. The coded weather forecasts were intended for Japanese diplomats working overseas and alerting them to an imminent attack. If within the weather forecast a message stated "North Wind, Cloudy" then it meant war with the Soviet Union. If the forecast included the words "West Wind, Clear" then it meant war with the British Empire. If the forecast included the words "East Wind, Rain" then it meant war with the United States.

Year 1941, a roll of film is delivered to Shanghai and a Chinese spy named Gong An Ming (Liu Yun Long) must decide what he should do with the film, which turns out containing a great secret that could shock the whole world. He discovers the plan code named 'East Wind Rain' and passes the information to the American that their territory will soon be invaded by the Japanese. The code is aired during the weather report from Radio Tokyo on Dec 4, 1941. While in Shanghai An Ming meets with a singer cum pianist, Huan Yan (Fan Bing Bing) and falls in love with her, not realizing that she is also one of the spies. Soon An Ming realizes that his effort found no success and have been ignored due to some reason. And now by risking his own life he must also decide whether to make Huan Yan his lover or his enemy? Will the Japanese attack Pearl Harbor in the end? Which country is Huan Yan working as a spy for? Will An Ming get caught by his enemy?