Meet the Sinister-Winterbottoms: brave Theo, her timid twin, Alexander, and their older sister, Wil. They're stuck for the summer with their Aunt Saffronia, who doesn't know how often children need to eat and can't use a smartphone, and whose feet never quite seem to touch the floor when she glides-er-walks. When Aunt Saffronia suggests a week pass to the Fathoms of Fun Waterpark, they hastily agree. But the park is even stranger than Aunt Saffronia....

 Twins Theo and Alexander and their sister Wil are abruptly dropped off at their Aunt Saffronia's house, where they learn they must complete a series of tasks in order to see their parents again--and their first assignment is at a waterpark. Conoce a los hermanos Sinister-Winterbottom: a la valiente Theo, a su tímido gemelo, Alexander, y a su hermana mayor, Wil. Los tres están atrapados durante el verano con su tía Saffronia, que no sabe cada...