Kidnap (2007)

Three years ago, drama teacher Lam Hiu Yeung (Karena Lam) lost her younger brother in a kidnapping case, headed by female inspector Ho Yuen Chun (Rene Liu). Three years later, she is now on the verge of another great loss: her husband is in the late stages of cancer, and options are running out. To take him overseas for medical treatment, she needs money, and a lot of it. Using what she learned from her brother's tragic incident, she calmly masterminds the kidnapping of a tycoon's son, a case that again falls into the laps of workaholic detective and divorced mother Yuen Chun. These two strong-minded women square off in a high-stakes battle of wits, but plans and composure melt away on both sides when they realize that Hiu Yeung has nabbed the wrong kid - Yuen Chun's son.