Martial arts students Lau Zhai (Yuen Biao) and buck-toothed So (Wu Ma), members of the esteemed Po Chi Lam school, put the school into a mess when the herbs they brought over from Hong Kong actually contain a large amount of opium hidden within the crates.  Lau Zhai takes the fall for the unfortunate mess and begins to track down the smugglers who are smearing his and, more importantly, his school's name.  He soon discovers that old friend Ming is working for secret opium impresario Chairman Wah (Yuen Wah), and poor Lau Zhai must team up with the local constable, Panther, and go undercover within the criminal organization to get proof of their nefarious activities.  But, going undercover means he must go it alone, separate himself from his school and friends, and play at being a bad guy while receiving scorn from his buddies.  But, when Chairman Wa discovers Lau Zhai's ruse, it may be too late.