When his sister disappears, Noah, along with their best friends, Ella and Richie, sneak into the neighborhood zoo and delve into the unknown world of the animals, where they discover a great secret that the zoo is protecting.

"On Halloween night, the scouts, along with their Descender allies, must battle terrifying sasquatches at their own elementary school. Little do they know, the sasquatches are merely the bait to a trap. DeGraff captures three of the Descenders and drags them into a frightening, off-limits sector of The Secret Zoo. Meanwhile, Noah and his friends must protect two of their animals allies from police officers who are convinced that they are dangerous...

"Hidden beneath the regular Clarksville City Zoo, the Secret Zoo is an incredible world where animals and humans peacefully coexist as equals. But even in the Secret Zoo, there are dangers and forbidden places. When Noah and his friends discover tarantulas roaming around, they're sure the bad omen can only mean one thing: the Shadowist is nearby. Closing the portals is the only option to save all the animals at Clarksville City Zoo...But when Mr....