Henry, Jessie, Violet, and Benny used to live alone in a boxcar. Now they have a home with their grandfather, and they're spending a week at Camp Seagull on beautiful Claw Island.
When they arrive at Camp Seagull, the Alden children look forward to a week of new friends, exciting activities, and most of all, the annual camp Olympics. But as soon as camp begins, Henry, Jessie, Violet, and Benny realize that someone is not playing fair. Everything begins to go wrong for the Aldens -- they lose their luggage, Henry misplaces the camp flag, and campers on the other team use one of Jessie's ideas to score points for themselves. Are some campers so desperate to win the Olympics that they are willing to cheat? The Boxcar Children are determined to solve the mystery before the competition is ruined for everyone!