Killer Instinct

Published in 2014, Killer Instinct is the second installment in Jennifer Lynn Barnes’s The Naturals series. The young adult series follows narrator and protagonist Cassie, whom the FBI recruits as part of a program for gifted teenagers due to her keen profiling abilities. In Killer Instinct, she and the other members of the Naturals program—her friends Dean, Michael, Lia, and Sloane—investigate strange murders that mimic those committed by Dean’s father, a notable serial killer who is now incarcerated. The story explores The Impact of Trauma on Behavior and Emotional Intelligence, Moral Dilemmas in the Face of Danger, and the significance of Biological Heritage Versus Found Family. 

This guide refers to the 2014 Kindle edition of the novel.

Content Warnings: The source material and guide feature depictions of graphic violence, death, child death, physical and emotional abuse, and child abuse.

Plot Summary

The beginning of the story picks up after the events of The Naturals, in which 17-year-old Cassie Hobbes was recruited into the secretive Naturals program. In the process, she learned that her aunt, Lacey Locke, was a serial killer that the FBI had been investigating; Locke was killed at the end of the first book after trying to rally Cassie to her cause. Killer Instinct begins a few weeks later, as Cassie struggles to come to terms with these events while resuming her work with the Naturals.

When Cassie and the other teenagers in the program—Dean, Michael, Lia, and Sloane—learn that a missing child named Mackenzie McBride was just found alive and well thanks to their effort, they celebrate with a party. However, they are interrupted by the arrival of Special Agent Veronica Sterling, their new supervisor. Her father, FBI Director Sterling, has just appointed her to assess the Naturals program. Sterling appears strict and off-putting, and she quickly antagonizes the teens. She forbids them from participating in any investigations until they have caught up with their academic work and requests that they all take GED practice tests.

Meanwhile, a young girl named Emerson Cole is murdered and left on display on the Colonial University campus. Sterling and Briggs, the other agent in charge of the Naturals program, are called to investigate. The crime scene bears a striking resemblance to the modus operandi of Daniel Redding, an infamous serial killer who is now incarcerated. Redding is Dean’s father, and Sterling and Briggs arrested him years earlier. Emerson’s murder and its connection to his father’s crimes strongly impact Dean, causing him to isolate himself. Over the course of the story, Cassie learns more about Dean’s past and the investigation that led to Redding’s capture, including the fact that Redding occasionally encouraged Dean to participate in murders. When the FBI started catching up to him, Redding abducted Sterling, intending to kill her, but Sterling and Dean escaped together. The Naturals program was then founded to help young people like Dean, whose traumatic pasts led them to develop natural talents in profiling.

Wanting to help Dean overcome his traumatic memories, Lia recruits Cassie and Michael to pursue their own investigation at a Colonial frat party. There, they meet Geoffrey, an arrogant and coercive teaching assistant for Professor Fogle’s criminal psychology class on serial killers. Geoffrey shows Cassie and Michael one of Fogle’s lectures on Daniel Redding and seems to openly admire the murders. The three Naturals also meet Derek and Clark, two students from Fogle’s class who knew Emerson and seem to be hiding something. Having identified potential new suspects, Cassie, Lia, and Michael return home and swear not to tell Dean about the risks they took.

The FBI reaches out to Redding to get his opinion on Emerson’s murder, but Redding only agrees to talk to his son. Dean asks Cassie to accompany him, Briggs, and Sterling to the prison for moral support. Sterling and Cassie wait in the car while Briggs and Dean go talk to Redding, but an overzealous prison guard named Webber insists on checking out Sterling and Cassie’s credentials. He makes them wait in an observation room from which Cassie witnesses the conversation between Dean and Redding. Redding reveals that he knows Fogle and provides information about a remote cabin that the professor owns. After Cassie tells Sterling about Geoffrey, Clark, and Derek, Briggs reveals that Redding mentioned that a student of Fogle’s sent him letters.

Later, Sterling and Briggs find Fogle dead in his cabin. Now with two victims to investigate, Director Sterling asks the Naturals to monitor Fogle’s students’ social media to find leads. They find Clark particularly suspicious but quickly realize that footage from Fogle’s class provides all his students with an alibi for Emerson’s murder.

The next day, Dean, Cassie, and Michael drive to Dean’s hometown to speak to Trina Simms, a woman who is in a romantic relationship with Redding. She appears naïve and cruel but ultimately harmless. However, her son, Christopher, seems strangely hostile and violent, which makes him a suspect. When the teenagers go back home, Sterling is angry that they went out in secret again, but a notification that Trina Simms was just murdered, and Christopher has an alibi, soon distracts everyone. 

The crime scene reveals that Redding has been orchestrating the murders from prison. When the FBI asks to speak to him again, Redding insists on having Cassie interview him herself. Redding’s answers prompt the Naturals to realize that Redding has more than one apprentice and that they are looking for two murderers, each of whom killed the other’s victim.

The FBI then learns that Clark, one of its main suspects, has just been murdered. The FBI goes after Christopher, the second killer, and arrests him just as he is about to attack another victim. Based on the pattern of choosing victims, however, Cassie realizes that the plan must involve a third apprentice. Before she and Sterling can warn Briggs, they are abducted by the third killer, who is revealed to be Webber.

Having now grown into his own serial killer persona, Webber ditches Redding’s MO. Instead, he takes his hostages to a remote location, frees Cassie, and tells her to run so that he can hunt her through the forest. Cassie fights him off, but Webber overpowers her. However, Briggs and Dean arrive just in time to save her. After Briggs shoots Webber, Dean and Cassie kiss, finally cementing their relationship.

At the end of the story, Sterling moves into the Naturals’ house, having decided to embrace the program. The teenagers will now be allowed to work on active cases, and Cassie plans on continuing her investigation into her mother’s disappearance.