When nine-year old Elisabeth Vanklewen and her best friend Eveline Brighton (the Clue Duo) decide to attend a rubber duck river race to raise money for their school, St. Angelica Elementary, they discover their third mystery, and it really seems like they are out of ""duck"". But with a stream of suspects and 2000 rubber ducks you are never really out of ""duck"". Join the Clue Duo as they ""quack"" this case and discover that sometimes the answer to a problem is not clear... it's muddy.