Cursed by an old carnival game, sixth-grader Rex Dexter uses his new ability to communicate with dead animals to investigate the mysterious deaths of endangered zoo animals.

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...

Eleven-year-old Whit's zookeeper parents have rarely allowed him to go outside of the Alabama zoo they run, but he stops seeing it as such a cage when he meets "Bird Girl, for whom the place is a refuge from problems at home.