In Shanghai in 1937, Su Qingyuan, a female radio anchor who returned from studying abroad, conveyed warmth through the airwaves every day, but she did not know that her voice had already become a "life-saving signal" for Lu Shiyan, the underground party liaison officer - he could always decipher important information from the subtle noise after she told the time.
In an accident, Su Qingyuan discovered Lu Shiyan's secret, and the two were forced to bind: she used the broadcast studio as a cover, and he used radio waves to convey his faith. In the war of troubled times, the late-night radio band became their only connection. "It will rain tonight, remember to put on more clothes" is a common advice and a code of life and death.
As war approaches and the radio station is monitored by the Japanese army, they must choose between the justice of their family and the love of their children. In the last broadcast, Su Qingyuan sang the song of the first meeting softly into the microphone, while Lu Shiyan held the gun tightly on the other end of the radio wave: "Wait for me, let's listen to the sunny day without noise."
