When Callie and her parents move from the country to a new home in the city, she is not sure she will be happy. When they get to the city, though, it's nothing like she thought it would be. She is surprised to see lots of beautiful trees. Then she discovers that the big tree in her front yard is very special! Baxter the bur oak teaches Callie about the good things he does for her home, and his acorn friend Mac takes her on a fun adventure around the city!