The book was followed by a sequel, Game, where Billy has escaped from prison. The NYPD turns to Jasper after a series of murders committed by the Hat-Dog Killer take place. Jasper soon learns that the Hat-Dog Killer and his father are connected, as well as the possibility that his Missing Mom may still be alive.
The trilogy concludes with Blood of My Blood, where Jasper is framed for the murder of Agent Morales. Jasper must escape from New York City in order to bring Billy to justice once and for all, but on the way, he learns about an organization of killers called "the Crows."
I Hunt Killers provides examples of:
- Abusive Parents: Billy is, believe it or not, of the emotional variety, as he claimed that he never spanked Jasper. However, he compensates by exposing him to the life of a serial killer. Janice Dent is later revealed to have sexually abused Jasper and even thought about killing him at some point.
- Arc Words: "People are real. People matter."
- Ax-Crazy: The Impressionist and both halves of the Hat-Dog Killer are this.
- Berserk Button: Getting compared to Billy is a quick way to piss Jasper off.
- Big Applesauce: Book 2 and 3 are set in New York.
- Black Widow: Billy is believed to be this until the end of book 2. Duncan Hershey attempts this.
- Consulting a Convicted Killer: In each book, Jazz needs to consult Billy, whether it's about a case or about his own upbringing and unfound victims.
- Even Evil Has Loved Ones: In some twisted way, Billy does care for Jasper, as he talked Janice out of killing him as a newborn. While he did try to kill Jasper in the third book, he decided not to expose Jasper as the one who crippled him in an act of vigilante justice. He was also against Janice killing his mother.
- Even Evil Has Standards: Billy apparently never targeted children during his killing spree. However, he wasn't against the idea of Jasper killing one of his childhood bullies.
- Both the Impressionist and Oliver Belsamo may be Ax-Crazy killers, but they adhere to a strict set of rules by Billy. Belsamo was also disgusted that he had to rape his victims after Hershey started doing it as part of the rules of Billy's game.
- Eviler Than Thou: Duncan Hershey believes he's this to Billy. Janice Dent really is.
- Great Escape: Billy escapes from prison at the end of Book One and Book Two and Three deal with the fallout.
- Heterosexual Life-Partners: Jazz and Howie.
- Insane Equals Violent: Everywhere.
- Loony Fan: The Impressionist and the Hat-Dog killer are this.
- Never Found the Body: Janice. Because she's Faking the Dead.
- Offing the Offspring: Duncan Hershey attempted to kill his child, along with his wife, but was stopped by Billy. Janice wanted to do this to Jasper, but Billy intervened.
- Our Slashers Are Different: Each book deals with a serial killer who likes to hunt and attack young people, especially women/girls. But Game and Blood Of My Blood reveals that [[spoiler:they are actually the member of
- Pet the Dog: While the amount of Dogs Billy has kicked drastically outweighs the ones he has pet, he still has a few. Mostly his mother and Jasper, though neither of them rise to Morality Chain level.
- Rape Is a Special Kind of Evil: Janice and Billy are both vicious serial killers, but the real twist appears to be when it's revealed that Janice sexually abused Jazz.
- Serial Killer: Obviously, in spaces.
- Unholy Matrimony: Billy and Janice.
- Wounded Gazelle Gambit: Janice attempts to pull this on Jazz and Connie. It works for a brief time.
- You Have Failed Me: Why Janice tries to kill Jazz.