Following the publication of her fifth novel, 2013’s The Widow Tree, Nicole Lundrigan took a break from writing. “I felt drained of ideas,” she acknowledged in a blog post on her website. Eventually, however, she began to hear the voice of a character she felt to be “the most complicated individual [she] has ever tacked down to paper.” That character is a psychopath, one of the dominant voices in Lundrigan’s new thriller.

The Substitute tracks two parallel plotlines in alternating chapters – one from the close third-person perspective of Warren Botts, a scientist and PhD who has taken a leave of absence to teach middle-school science; the other the first-person voice of an unnamed teenager (the aforementioned psychopath) who views the world through a starkly unemotional lens. Warren is a “gangly spider” of a man, nervous and delicate, who calms his overactive mind by counting (foot taps, random objects, seconds of awkward silence). By contrast, the anonymous narrator – usually referred to as “Kiddle” by family members – is cold, calculating, and frighteningly callous: “I hated that word. Love. People tossed it around so easily, as though it was the epitome of existence. Common stupidity … a meaningless emotion.”

Despite their apparent differences, there are enough similarities between Warren and the anonymous terror that, for large portions of the novel, the reader is led to consider the possibility that they could be past and present versions of the same person. Both of their fathers are dead, both have troubled and burdensome younger sisters, both are emotionally neglected by their mothers. Despite the apparent discrepancy of the unnamed narrator’s sister dying as a child and Warren’s sister being a drug addict who is very much alive, Lundrigan casts enough doubt about the sanity of both her central characters that the reader is never fully able to distinguish between truth and delusion.

When one of Warren’s students is found dead by hanging in his backyard, the two narratives slowly meld to produce a scenario that even the most seasoned readers of crime fiction will have trouble anticipating. The clues are there, but they are sneaky and deceptive, and that is the true genius of the novel’s final reveal.

A minor quibble is that, because of the alternating perspectives, some of the middle chapters feel drawn out, with one character’s narrative arc slowing down while the other’s picks up steam, and vice-versa. Lundrigan’s prose is sufficiently sharp and biting, however, to keep readers interested, and her metaphors are fantastic. The anonymous narrator’s heart is “a fist-sized rock, covered in algae”; another character is described as “a drop of poison snaking through a pitcher of still water.” It is this kind of writing that places The Substitute above more commercial and pedestrian thrillers of The Girl on the Train’s ilk.

Lundrigan’s novel is a spine-chiller for readers who appreciate language and refined, well-crafted plots – and who aren’t afraid to delve, for a time, into the mind of a psychopath.