In a red apartment in New York, the dog Mike (voiced by Louis C.K. Louis C.K.) lives an ordinary and happy life with his owner Katie (voiced by Ellie Kemper). It doesn't understand why the owner goes out early and comes back late every day, and always hopes that Katie can accompany it all the time. That evening, the owner brought back a huge dog Du Lao Da (voiced by Eric Stonestreet), which made Mike feel like the sky fell. It tried to drive Du Lao Da away, and the other party also used it to fight back. In the process of fighting, the two little guys were surrounded by the dog catching team. During this period, they met the fallen pet gang led by the rabbit Xiaobai (voiced by Kevin Hart Kevin Hart) and experienced an unprecedented adventure. On the other hand, Mike's secret admirer Chuchu called on his partners to save his kind and amiable friend. When the owner was not at home, the pets launched a thrilling battle...