The Frisbys have been growing money for ten years, concealed from their island friends and neighbors. Jane tolerates the temperamental money tree (George's pride and joy) while worrying about the effect of secrecy on the children. 18-year-old Daffy understands the threat the tree represents, but still wants to give seedlings to families in need. Her 12-year-old brother Mike wants to franchise them.

In Washington, the Secret sSrvice is investigating stories about a new counterfeit source. A plan is put in motion to acquire one of these bills even as Daffy and Mike capture an intruder, David, who claims to know their father.

George recognizes David from an Amazon expedition years ago and invites him to stay for a few days. Jane resolves to keep him until Christmas, when the harvest is processed. And so life goes on, while the net draws tighter around the Frisbys and their guest.

A Secret Family Harvest explores the value of money and family, and how secrets can really mess with you, especially when you're growing up.