"Zoo" episode 5, "Blame It On Leo," featured Chloe, Mitch, and Abraham while venturing into Rio De Janeiro, while Jackson and Jamie went their separate ways to look for Leo Butler. Butler was a former Reiden Global staff who was blamed for concocting the bacteria that was responsible for the sinister behavior of the animals.
In an attempt to study the blood sample that he collected from a wolf in last week's episode, Mitch breaks into a college science lab in Alabama to use the equipment. He then discovers that the bacteria caused the animals afflictions, a work all pointed out to Butler.
While this is happening, Jackson notices that Butler's name appears several times on pages on Evan Lee Hartley's Bible. After this discovery, he insists on being left behind in Alabama to go look for Butler while the rest of the group heads on to Rio De Janeiro to look into reports of a swarm of bats that are attacking the city. Chloe gives in to their request and Jamie and Jackson stay behind while she, Abraham, and Mitch continue with their plans to go to Rio De Janeiro.
Mitch's professional and personal life collides as he struggles with a decision that involves his dog Henry. A little girl named Clementine Lewis plays with Henry and upon sensing that there was something wrong, he barks loudly and warned the girl's mother, Audra Lewis, and his stepdad, Justin Lewis, of an epileptic seizure that the little girl is having.
Henry somehow escapes from the backyard and gets hit by a car. The family is now faced with the problem of paying for their daughter's medical care, as well as, the cost of Henry's surgery. Justin then tries to convince his wife to get assistance from her ex-husband to cover for Henry's medical bills but she refuses. They then agree to take care of Henry's vet bill and hope to be able to deal with whatever will come along later on.