Mitch is examining the bacteria collected from the hotel at a high school science lab in Alabama, as Jamie rushes him. Mitch discovers that the bacteria happens naturally, a chemical signature, based on the food chain. The chemicals were consumed naturally, but then as other animals ate their prey, the chemical spread. Jackson is going through Evan's bible, and notices that Evan has written the name “Leo Butler” all over his bible.
Chloe announces to the group that they are headed to Rio...there are swarms of bats everywhere there, in daylight. Jackson doesn't want to go to Rio, he'd rather head out in search of Leo Butler. Mitch receives a phone call from a contact at MIT who is looking into the chemical stamp on the bacteria. It turns out, the chemical stamp is from Reiden Global, and the scientist is none other than Leo Butler.
While Mitch shares bat facts with Abraham and Chloe on the plane to Rio, Jamie and Jackson are researching Leo Butler. He has been blackmailing Reiden Global since he stopped working for them. Agent Shaffer comes to their hotel room...he knows that Jamie hacked the Reiden Global, and he wants to know why. Meanwhile as the others' flight to Rio lands, they see that the bat situation is worse than they thought.
In Boston, a little girl is reading the latest issue of a teen mag to her dog, when her dog begins barking madly. The little girl, whose name is Clementine, is having a seizure, and the dog, Henry, has alerted her family in time to save her.
Jamie and Jackson have filled Agent Shaffer in on Leo Butler's identity, and he is going with them to question and arrest him. Leo tries to run when they arrive at his house, but Jackson punches him, and knocks him unconscious. When Leo wakes up, Jackson begins questioning him. How does he know Evan, does he know Robert Oz? Leo knows nothing. Jamie wants to talk to Leo about Reiden Global... he doesn't want to talk to her until she tells him that she is from Folsom, Lousiana.
Chloe wants to know if there has been any testing on the bats in Rio...they do not have rabies, but are still causing a number of issues. The government in Rio wants to spray a drug over the city to kill the bats, which will also cause harm to the citizens. Mitch and Abraham notice that the bats are only swarming select areas of the city. Upon investigation, the bats are swarming over a bad and polluted part of the city. The bats are congregating on the transformers, chewing at the wires, until all of the electricity is out. A truck with a gang of locals approach them, and threaten them. Abraham wants no trouble, but Chloe pulls out her gun, as do they. Abraham pays them off and they leave.
Back in Boston, Henry has gotten out of the backyard. As the little girl, who we find out is dying, worries about her dog, her mother gets a phone call from the girl's step dad... Henry has been hit by a car, and he is taking him to the vet.
Chloe and Mitch are examining the dead bat collected after the gang standoff, and Mitch confronts Chloe on her lack of field experience, considering she is their field leader. She assures him that she is well trained to do her job, to which he says sounds like it came from a spy novel. She wants to meet the person who made him so cynical. Mitch notices that the pupils on the bat are changing, getting bigger, changing shape, when suddenly the bat's eyes open, and it flies around the room. The dead bat is not dead anymore.
Leo begins to share his story with Jamie, Jackson, and Agent Shaffer. They tell him about their hotel room coffee pot experiment with the bacteria. Leo says the reason that Reiden Global is the top company is that they have a vector... the vector is a DNA molecule that allows them to be faster and cheaper. They call it the Mother Cell and its top secret. Reiden knew that the Mother Cell had side effects, but they had already invested so much money that they let it go. The side effects are doing something to the animals, and it doesn't stop there. The Mother Cell is everywhere, in every product Reiden makes. The Mother Cell is too powerful. It cannot be stopped.
Leo knows how to get this Mother Cell, the vector that he's spent so many years blackmailing Reiden over. But he won't share its location, or get it. Jamie offers to go with Leo alone to get the cell. Leo agrees.
In order to save Henry, Clementine's parents have to pay $3,000 in follow up visits. Her step-dad wants to ask her father for the money. Her mother objects... she hasn't seen her father since she was two. They can't afford it, but they will make it work. They can't let their little girl lose her best friend.
Chloe calls Jackson to complain about Mitch, and update him on their progress. As she is outside on the balcony, a bat attacks her. She drops her phone on the balcony, and the bat swarms to it. It flaps over it, and then flies away. Chloe hangs up on Jackson, and poses the theory to Abraham and Mitch... was the bat attracted to her cell phone? The bats were also attracted to the solar panels and to the electrical poles. Mitch begins to explain the trophic scale, and why humans, who are actually very low on the scale are able to behave like they are at the top. It is because of their reasoning and their technology. Chloe comes up with an idea. If they set a trap, so that they are too far out for the bats to see, and they send out an antenna signal to see if the bats respond to it.
Agent Shaffer is GPS tracking Leo and Jamie, and Jackson decides to snoop around to try and find out why Leo's name was all over Evan's bible. Leo drives out into the wilderness, and parks the car. He gets out to get the Mother Cell, leaving Jamie alone. Jackson comes across an inventory list of what chemicals made by Reiden Global have the Mother Cell, and what it was used for. The Mother Cell is in almost everything from food animals eat, to human food. Leo returns with the Cell. He passes it off to Jamie, relieved to finally be rid of it. He says it's their problem now.
Clementine is loading up a box of clothes. She wants to sell them to contribute to Henry's vet bills. Her mom finds a photo of Clementine's dad. She asks her mom if she got sick enough, would her dad come back? Just then, her step-dad returns with Henry, who is on the mend. They go off happily to play together. Clementine's mom looks back at the photo... it's Mitch, holding Henry as a puppy. Clementine's medication is next to the photo, and those meds are distributed by none other than Reiden Global.
Abraham, Chloe, and Mitch set out on their experiment. As Mitch and Chloe set up, Abraham steals a car. The gang from earlier approach Chloe and Mitch, who try to tell them that they are just trying to solve their bat problem. Without Abraham there to intervene, things get violent.
Leo shows Jamie a boat on his cell phone that he wants to buy when this is all over. She says she wants to go sailing with him. He tells her she doesn't need to turn on the charm anymore. He realizes that his GPS is on, and that Agent Shaffer and Jackson are tracking him, and thinks Jamie tricked him. As she protests, their car is hit by another. As Jamie wakes up from the impact, she sees that Leo is unconscious. She sees a set of footprints approaching the car, and Evan appears to ask her where it is. She says nothing, as he reaches into the car, and takes the Mother Cell.