1937年哈尔(ěr )滨遭日(rì )殖民统(tǒng )治,日伪残酷围剿抗日力量。哈(hā )尔滨口(kǒu )琴社实(shí )为中共地下情报据点,秦娜带(dài )领社员(yuán )以演奏(zòu )为掩护,秘密传递情报,开展抗(kàng )日斗争(zhēng )。日伪突(tū )袭据点时,秦娜沉着周旋,特务(wù )科副科(kē )长陈宇(yǔ )暗中掩护,口琴社暂脱险境。义(yì )士沈岩(yán )刺杀汉奸后,因妹妹沈玲的抗日赤诚(chéng ),投身地(dì )下斗争。众人组装高频干扰器(qì )反制日(rì )军电波(bō )侦测,顾晓雄奏响抗日旋律遭(zāo )捕,受尽(jìn )酷刑后(hòu )壮烈牺牲。秦娜传递关键情报(bào ),多位战(zhàn )友殉国(guó ),她将情报融入乐曲,登台传递(dì )后英勇(yǒng )就义。沈(shěn )岩铲除日寇指挥官铃木康,最(zuì )终与松(sōng )田同归于尽。沈玲在陈宇的掩护下成(chéng )功发报(bào )撤离。以口琴社为核心