Max (Louis C.K.) is a spoiled terrier who enjoys a comfortable life in a New York building until his owner adopts Duke, a giant and unruly canine. During their walk outside, they encounter a group of ferocious alley cats and wind up in a truck that's bound for the pound. Luckily, a rebellious bunny named Snowball swoops in to save the doggy duo from captivity. In exchange, Snowball demands that Max and Duke join his gang of abandoned pets on a mission against the humans who've done them wrong.