Director Lung Kong blended these trends into the social-issue dramas which he had already made his speciality with late 1960s Cantonese classics like "The Story of a Discharged Prisoner" (1967) and "Teddy Girls" (1969). In the 1970s, he began directing in Mandarin and brought exploitation elements to serious films about subjects like prostitution ("The Call Girls" and "Lina"), the atomic bomb ("Hiroshima 28") and the fragility of civilised society ("Yesterday, Today and Tomorrow" (1970), which portrayed a plague-decimated, near-future Hong Kong) (Teo, 1997).