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 animal allies from police officers who are convinced that they are dangerous...

Noah, Megan, Richie, and Ella must navigate a maze of never-ending aquariums in the Secret Zoo to rescue their animal friends.