A career-long undercover Hong Kong cop is sent to Mainland China when his former protégé becomes the primary suspect in a murder. A career-long undercover Hong Kong cop is sent to Mainland China when his former protégé becomes the primary suspect in a murder. A career-long undercover Hong Kong cop is sent to Mainland China when his former protégé becomes the primary suspect in a murder. A career-long undercover Hong Kong cop is sent to Mainland China when his former protégé becomes the primary suspect in a murder.