Twelve-year-old Kip is spending the summer with his grandmother and his five cousins, all of whom are full of enthusiasm, action, and talk. His mother has just remarried and he is not sure what life will be like when the newlyweds get back from Hawaii. Gran's seaside home is like nowhere else. The house has been sold and will be demolished soon so Kip and the girls are free to write on the walls, paint them, and bash them with sledgehammers if they wish, and the cousins do so with gusto. The onslaught of the girls takes a while to adjust to, but Kip has the attic bedroom as his retreat. There he finds his deceased father's adolescent journal, a notebook filled with a story of espionage, secret plots, and a boy called the Operative. Kip feels an instant connection to this story and comes to see that Tristan was the same sort of kid that he is.