Coop for Keeps is a story about trust and belonging told through the viewpoint of Coop, an old dachshund. After the death of his former companion, Mike, Coop is adopted by Mike's daughter, Jess, and her children, Zach and Emma. Coop feels like a misfit and an outsider in the family, especially when it comes to getting along with 14-year-old Zach, who is having adjustment issues of his own.

When visitors arrive at Jess's newly opened guest house, conditions worsen. The situation sours even more when 5 crows arrive to compete for Zach's attention, and bully brothers, Dylan and Donnie, along with their mean dog Biggie, harass and threaten Zach and Coop, resulting in Lucinda, the family's pet cat, running away.

Can Coop and Zach work together to find Lucinda, settle matters with the bullies, and establish a friendship of their own?