Flynn speeds on a motorcycle and tortures himself about letting Abby go, and still loving Abby, and not knowing if Abby still loves him. Abby! Abby! Abby! He crashes his motorcycle 'cause he's wasted. Briggs ponders whether he'll still be a useful teammate, to which Jackson ominously says that if he isn't, they'll "pull the plug."
Emme tells Flynn she's pissed that he risked his life and looks for something to cut herself with. In the garage, she finds classified files detailing Abby's Hunter secrets! Her life sucks.
Briggs shows up at Flynn's house and demands to talk, interrupting Flynn's big plans to booze and pop pills for the rest of his life. Flynn begs Briggs to kill him and claim it was self-defense, but Jackson appears and takes Flynn for a ride. He shows Flynn his file from after he escaped the Hunters in Afghanistan. They did something to him and he must come to terms with it or it will kill him.
At the ETU, Regan lovingly interrogates Ted, her father, who doesn't know anything about The Purge or Viktor Karp, an arms dealer who has access to long-range missiles. Finnerman assigns Regan to apprehend her mom Liana in exchange for her dad's release.
At the Hunter base in Mexico, Liana is pissed that Sterling Martinez can't get a Hunter to revert to its native form. She threatens to tear his face off if he can't figure it out.
Regan arrives in Mexico. Guys with guns show up, put a sack on her head and take her to the Hunter camp. They strip-search her and she meets Viktor Karp, who is just plain rude. She tells him that she's left the ETU and wants to meet with Liana. Karp says that Liana doesn't have a daughter and his goons knock her out.
Later, Regan wakes up and Karp tells her that her story checks out. She convinces him that she wants to join the Hunters as he takes some of her blood. What's up with that? Later, Regan sees the Hunters packing what looks like a giant missile on a truck to send to Musa.
Karp takes Regan to a barn to see Liana, who doesn't buy Regan's story about wanting to join the Hunters. Liana then asks for a hug, which is terrifying. When Regan softens, Liana attacks her. So mean, but Regan whups her good after she rips a gun from the wound in her own back (!) and shoots Liana across the room.
Regan runs out of the barn, but Liana jumps her, furious that she would use her child pouch to hide a weapon. They fight fiercely. Regan makes a run for the road, but she ain't safe, 'cause Liana makes Jason Voorhees look like Shrek. She shows up with the giant-ass gun, but right as she's about to shoot a truck drives by and Regan disappears. You know what they say about apples and trees ...
Meanwhile, Sterling Martinez's work in reverting the Hunters is finally working. The creature in the Hunters' lab comes out of its human shell to reveal itself in all of its glory, actually looking a lot like the monster that Craig T. Nelson vomited up in Poltergeist II: The Other Side. It was gorgeous in 1986 and so it remains.
Liana tells Abby to kill Sterling now that he's fulfilled his purpose. Sterling moves Abby as he muses about the amazing things that can happen when humans and Hunters work together. He doesn't see Hunters as monsters, but as misunderstood. She breaks his neck, but she's sad about it.
Regan returns to the ETU and gives Finnerman all of the intel, but Finnerman still won't free her father since she didn't apprehend Liana. Regan goes to visit him in the interrogation room. Ted apologizes for not protecting her and tells her that as long as he's alive she won't be safe because the ETU will keep using them against each other. He reveals that he's stabbed himself and urges her to "protect the innocent ones." Regan cries out for help as her father bleeds all over the place.