There's nothing magical or mysterious about 6th grade for Tessa and Gus, but summer's coming and that means trash hunting, basketball in the alley, and best of all, no school. This summer holds so much for them, and when their mysterious neighbor Professor Henchworth gives them a magical spyglass called a vider, a new adventure begins. The vider shows them things are not as they seem: a brilliant Unseen world surrounds them - and it's in danger! If the Unseen disappears, their world will too. Only Tessa and Gus can prevent disaster, but sinister Shellstalkers spring up at every turn, and time is running out. With help from Gus's little brother, the kids must race to save life as they know it. Will they make it in time before people they love
disappear for good?