The story begins with Max who is a spoilt dog and he is the favorite pet of his owner. He believes in enjoying every moment of his life in the New York City with his owner. He lives in the New York building and his life is so comfortable until Duke decides to bring up trouble in his life. He adopts Duke, a big and giant Dog.
The two fight a lot in the beginning but one incident changes them and they have to put an end to their fights and hatred. One day, when they go out for a walk they are encountered by a group of wild and cruel alley cats. But fortune favors them and a cute and lovely bunny named Snowball jumps in to save the two doggies from the terrific and ferocious cats. Snowball saves them and asks to join the group of pets who have been abandoned and says that they are on a mission. Their mission is against all those miserable humans and their happily living pets.