Twelve-year-old Annie Lamm's first day of summer break quickly turns into a disaster. She realizes that her parents have not only decided to fly her to Hilton Head Island during their second honeymoon, but they also plan to coerce her to spend half her summer with her 76-year-old Grandpa Donald whom she hardly even knows. The place where Annie is staying, Grandpa's "beautiful house right by the beach", turns out to be a dilapidated and neglected dwelling filled with stored newspapers and dust covered knickknacks. Nothing edible is in the fridge, and only big-band and Perry Como records sit by his prehistoric stereo. Annie's summer plans of parties and boys are dashed in an instant -- Grandpa's house has no TV, no computer, and a swimming pool half-full of brown, brackish water with turtles living in it. His life consists of napping, doing crosswords and spending time with an old, codger named Barney with whom he trades endless tall tales. Annie is miserable! She calls her best friend, Holly, and asks her to investigate Greyhound bus schedules back to New York. In between suffering through Grandpa's outlandish tales of killing ten-foot snakes, seeing patriot raider ghosts who haunt the Island, giving batting lessons to Mickey Mantle and working security for Elvis Presley, Annie discovers Grandpa's tiny fishing skiff, covered in barnacles. Grandpa Donald tries his best to capitalize on any opportunity he can find to bond with his granddaughter, but Annie is reluctant. How could this man who is six times her age be anything remotely near the fun she could have had in New York with all of her friends? Intensely bored and fed up, Annie makes a plan to run away from the Island by motoring off in Grandpa's boat to the Greyhound station. It turns out to be the decision of her lifetime. Annie's summer break, seemingly ruined at first, becomes a summer that she, her family, and her new friends will remember for the rest of their lives.