When undercover cops start losing their lives to drug lords who blame their demise on "poor acting", the Police Force counters by sending Hong Kong's Finest to acting school.

After successfully designing the perfect bra, Lena, Johnny and Wayne are ordered to come up with a marketing plan for the "Mighty Baby" line of baby care products. Johnny's life is complicated when he hires quirky secretary Sabrina. As for Lena and Wayne, their relationship is threatened when Lena discovers that Wayne is afraid of babies. To help Wayne overcome his fear, Lena hires child expert Boey. Unfortunately for Lena, Wayne starts to develop feelings for Boey.

The story revolves around a Spring, a hitman from mainland China who is on a mission in Hong Kong with his partner Setting Sun. However, Spring falls ill and comes under the care of a screenwriter by the name of Soya and they find themselves developing into a tight and everlasting friendship.