1941, Shanghai occupied area. Shen Qinghe, a primary school teacher with a meek appearance, turns out to be a radio operator for a secret radio station of the underground party of the Communist Party of China. Under the shadow of death of the Japanese and puppet "radio detection vehicles" patrolling day and night, he must use the most basic parts to keep the radio running and deliver key intelligence under the eyes of the enemy. Tonight, he received an encrypted message, the content of which would determine the life or death of an important figure. Next door, a newly moved Japanese businessman was holding a banquet, and the gendarmerie came uninvited.
