With Katie (Ellie Kemper) now married and raising a child, Max's (Patton Oswalt) family has grown even larger, and so have his fears. With the responsibility of protecting his new charge, the stress and anxiety begin to weigh in on Max.
Looking for some R&R, Katie takes the family out to the countryside for a vacation where Max meets a farm dog named Rooster (Harrison Ford). Under his guidance, Max works towards overcoming his fears.
Elsewhere, the rest of Max's friends in the apartment building are up to their own adventures as Snowball (Kevin Hart), Gidget (Jenny Slate), and Chloe (Lake Bell) find themselves looking to help out their friends. Gidget recruits Chloe to recover Max's favorite toy from a cat-filled apartment, while Snowball must become the superhero that his owner dresses him as in order to help out new apartment resident Daisy (Tiffany Haddish).