In 1983, Dave and Colleen Tillman were murdered, along with Dave's brother and his wife. Suspicion soon fell on Dave and Colleen's adopted son, Rusty. Rusty was a scary kid, into heavy metal and devil worship. The testimony of his adopted brother Dustin and cousin Kate, one of the other couple's twin daughters, helped get him a lifetime sentence for murder.
Thirty years later, the Innocence Project helps to get Rusty's conviction overturned and he's released from prison. Dustin, now widowed and a therapist living in Cleveland, is disturbed at the thought of Rusty back out in the world. What will he want? What could he still do? Falling in with his new patient Aqil Ozorowski, Dustin begins an investigation of Jack Daniels, a potential serial killer thought to be responsible for the drowning deaths of a number of college-age men. Meanwhile, Rusty reaches out to Dustin's sons Dennis and Aaron. Whatever his intentions toward the two younger men, they are already on a dark path. Aaron, in particular, is experimenting with harder drugs, and looks into a troubling case on his own when his junkie friend Rabbit disappears.
Ill Will provides examples of the following tropes:
- Alcohol-Induced Stupidity: The Jack Daniels killings are written off by authorities as this, as the victims had all been drinking, hence the name.
- Anachronic Order: Chapters jump backward and forward in time.
- The Cobbler's Children Have No Shoes: Dustin is a frequently tongue-tied talk therapist who helps people deal with their addictions. He has no idea his younger son is a heroin addict.
- Critical Psychoanalysis Failure: Dustin falls prey to the same obsessions that animate Aqil who picked him out knowing he'd be susceptible.
- Fake Memories: Both Dustin and Kate seem to have false memories regarding Rusty being the killer. They've been reinforcing these in each other since the time of the murder.
- Fingore: Rusty loses the tip of one finger at his job in a seafood restaurant. This parallels his late stepfather, who lost an arm from the elbow down.
- Heel Realization: Rusty remains angry at the people whose testimony put him away but he admits to some wrongdoing on his own part. Privately this includes his past sexual abuse of Dustin.
- Multi-Ethnic Name: Aqil Ozorowski: Middle Eastern given name often seen with African-Americans, Polish surname. He self-identifies as white, although Dustin isn't sure.
- Multiple Narrative Modes: There are several viewpoint characters, some of whom are given first person narration and some whose viewpoints are narrated in third person.
- The New Rock & Roll: The deaths of the four adults happened at the time of the Satanic ritual abuse scare, which was sometimes tied into heavy metal music. Rusty makes the perfect poster boy.
- The Unreveal: Several characters and events in the novel have gotten no resolution by the end.
- Wolf, the partner of Rusty and Dustin's cousin Wave, never appears and seems to really want to stay off the grid. It's possible he's involved in the events, but it's impossible to tell.
- Linda, the girlfriend of Dustin's older son Dennis, makes a couple of appearances in which she expresses an almost obsessive hostility toward Dustin. Is she deliberately trying to alienate him from Dennis.
- A park patrolwoman fires a gun at Aqil and Dustin. Aqil says she must have been part of the Jack Daniels cult conspiracy. To put it mildly he's not to be trusted on that, but there's not much other explanation for her going off.