Ming Chu (Ching Li) is dazzling friends with her acrobatic kung fu when along rides the town elder Madame Liu (Lam Jing), mortally wounded by the evil Black Tiger Gang. On her deathbed Madame Liu recounts how long ago, bandit Pai Tien Wang lay siege to their city prompting General Liu Tsing (Fang Mian) to nobly sacrifice himself so his subjects could escape safely, while second-in-command General Liu Hai Te (Wong Ching-Ho) was entrusted with the city’s fortune in jewels. Now years later, the townsfolk have seen nothing of their treasure or General Hai Te, though Ming Chu suspects his daughter Qing Qing (Shu Pei-Pei) has some clue.
Qing Qing, a sweet girl with no knowledge of her past, is accosted by bare-chested Black Tiger thugs, whose mysterious, bird-loving leader manipulates events from his shadowy, Bond villain lair. Riding to Qing Qing’s rescue comes dashing hero Zhong Ying Long (Chang Yi), a lethally skilled swordsman who wields four blades at once, with whom she is instantly smitten. However, Ming Chu pops up alongside her colour-coded sisters Xiao Lan (Helen Ma Hoi-Lun) and Xiao Ehr (Jen Man-Jing) and kid brother Hsiao Ying (Cliff Lok), to kidnap Qing Qing again! Furthermore, Zhong is a little disconcerted to unmask one of the Black Tiger group as Wan Tai Zhi (Chiu Hung), his fellow disciple at the Da Law Martial Arts School.
Though seldom heralded by English-speaking fans, Hong Kong critics rank Hsu Cheng-hung among the key figures in Mandarin cinema. Born in 1935, Hsu apprenticed at other studios before joining Shaw Brothers as a cinematographer, screenwriter and assistant director. Upon being promoted to director, he delivered the studio’s first significant martial arts epic Temple of the Red Lotus (1964) along with fan-favourites like King Cat (1967), The Silver Fox (1968) and The Thundering Sword (1967) which marked the screen debut of his frequent leading man, Chang Yi. The Secret of the Dirk was Hsu’s penultimate film after which he supervised the Chinese version of Zatoichi vs. the One-Armed Swordsman (1971), then migrated to Taiwan where he started his own film company.
Hsu crafts a compelling story with pleasing twists and turns, though things do take a while to grow clear being overly reliant on flashbacks to answer the myriad mysteries. In his hands the serial-like plot unfolds through noticeably subtle acting, instead of the broad theatrical gestures common to this genre, which anticipates the revisionist likes of Crouching Tiger, Hidden Dragon (2000). Ching Li makes a splendidly feisty young heroine and her banter-filled relationship with Chang Yi’s morally upright hero is nicely drawn. Li had been acting since age six when venerable Shaw filmmaker Chang Cheh noticed she had a rare beauty suitable for both classical and contemporary film roles. She was also a favourite of Chu Yuan, who cast her in over twenty of his films including the much beloved House of 72 Tenants (1972).
The action is consistently brisk and exciting, with the bloody finale proving the most suspenseful set-piece. Yet for such a seemingly light-hearted movie, this blithely massacres two-thirds of its cast before the painfully poignant fadeout.