Xia Tian, Jia Jiang, Fang Wei, and Bulu all grew up on Westside Street together and currently study in Ying Ye School and are one month away from graduation.

Xia Tian's dad is a police officer in Westside Street and is retiring tomorrow. But on that very day, they all had a fight at school with the Dinosaur gang, and were almost expelled by the principal. Officer Xia went to settle the conflict and not only did it not get settled, his gun got misplaced by the principal too. Everyone thus discussed things, and decided that they all will remain in the school, including Ah Jiang, and they must find the gun within one month of graduation to let Officer Xia retire peacefully and happily. Jia Jiang, Fang Wei and Bulu can then successfully graduate.