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.

Noah and his friends in the Secret Society join forces with four teens known as the Descenders to try to protect the Secret Zoo hidden below the Clarksville City Zoo from monstrous sasquatches and the evil Shadow Master.

"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...