How hard can it be to go back to your old job? Law Yiu Wah (Moses Chan) was a teacher at a dangerous high school before he was forced to resign over a peeping Tom controversy. Wah becomes a police officer but then is asked to go back to his old high school to investigate a triad drug network at the school. Working undercover, Wah meets new teacher Ho Miu Suet (Tavia Yeung) and clashes with Inspector Ching Man Lik (Ron Ng), the liaison officer at the school. Suet tries to boost her students’ confidence by bringing in bowling expert Koo Ka Lam (Linda Chung) to teach the kids how to bowl. Knowing Lam’s past ties to the triad, Wah takes a special interest in her. Meanwhile, Lik takes a liking to Suet, but she only has eyes for Wah. Can Wah get his job done by keeping his personal feelings in check and without blowing his cover? “Yes, Sir. Sorry, Sir!” is a 2011 Hong Kong drama series.