Tie shou wu qing zhui hun ling (1978)

An assassin terrorizes the countryside, killing many fighters from distinct clans and leaving only one clue - a mask. A secret government agent (Don Wong Tao) posing as an assassin, is on assignment to bring the assassin to justice. Meanwhile, Wan Yi Fei (Chen Sing) and his brother Wong Tu Lung (Wong Hap) are attacked and killed along with many other of the clan.