In the enchanting coastal town of Rivertide, four young friends—Roger, Diana, Snubby, and Barney—embark on a thrilling summer adventure filled with unexpected twists and mysterious occurrences. As they witness a series of peculiar events, including explosions at a secret submarine base and strange activities at the old inn, their curiosity sparks a determination to unravel the truth behind the Rubadub Mystery. Barney, driven by his personal quest to find his long-lost actor father, immerses himself in the world of a Pierot show, unaware that it holds the key to unraveling the secrets that surround them.