This is book 2 in the series. When Aly, Cass, and Jack realize Marco is missing, the Kurai Institute sets off to try and find him. They find Marco near a river and he has found a wormhole where he believes is where the second Loculus is. The four children go through the wormhole and find that they are not in the modern world anymore.
Rating: 7/10 – There were some really slow parts in this book, and they didn’t reveal any answers until the very end. Besides this, it was well written and an interesting story.