本片讲述了一桩因“狗咬狗”引发的连锁故事。余峰（黄磊 饰）、亮亮（闫妮 饰）、余一诺（安吉 饰）家的小狗妮蔻，为了救主人被隔壁藏獒咬成重伤，有权有势的藏獒主人却对余峰一家百般刁难。面对种种不公，余峰不再忍气吞声，发誓要为小狗讨回公道，但柴女士（汤唯 饰）等人的出现，却让矛盾进一步激化......狗生不易，小狗愿意用生命守护我们，我们又能为它做什么呢？

Yu Feng and Liang Liang's puppy gets gravely injured while defending them from the neighbour's large and aggressive Tibetan Mastiff. The arrogant owner of the Tibetan Mastiff, however, refuses to take responsibility, and the police aren't of much help since no people were hurt. When push comes to shove, Yu Feng vows to fight for justice for his puppy.