City Under Siege (2010)

Sunny is a naïve circus performer who dreams of inheriting his father’s knife-throwing skills. However, his hostile colleagues continue to bully him, relegating him to a lowly clown. On a tour to Malaysia, Cheung and other performers discover a cave occupied by the Japanese army during World War II. Instead of finding treasure, the performers – including Sunny – are sprayed with a mysterious chemical that turns them into superhuman mutants…

• circus troupe
• martial arts
• mutant