Billy and his best friends Anna, Jimmy and Andy are looking forward to a summer exploring Waterfall Woods, discovering more about the magical creatures who live there and the Rhythm of nature that keeps their world, and ours, in balance. Then the woods come under attack from a mysterious red lady, forcing the Sprites and brothers Wilfred and Bilfred into hiding, and the gang rush to the rescue! But what could the red lady really want? Could she be connected to Bilfred's disappearance all those years ago? Can Billy and his friends uncover the truth and stop the red lady before the Rhythm is put in danger once again?