A dark psychological thriller, Beware That Girl marks a departure in style and genre for Teresa Toten, who garnered much acclaim for her 2013 Governor General’s Literary Award–winning YA novel, The Unlikely Hero of Room 13B. That book told a heartfelt, wry, and rewarding story about a teenaged boy dealing with obsessive-compulsive disorder. While mental illness figures in Toten’s latest effort, Beware That Girl is anything but touchy-feely.

Kate O’Brien is smart, tough, and – as she enters her final year of high school – single-minded in her determination to get what she wants: admission to Yale. Having spent the last five years in foster care, Kate knows how to work the system, and part of that has involved earning successive scholarships at better schools than she could ever hope to attend otherwise. Her latest stop on the scholarship train is Waverly, a prestigious private academy for Manhattan’s richest and brightest girls.

Kate has also developed an uncanny ability to read people, and she quickly zeroes in on the girl who will make her life easier: Olivia Sumner. Also in senior year, Olivia seems to have it all. She’s incredibly rich, gorgeous, and well connected. But she’s also a bit untethered: having spent most of the previous year absent from school (euphemistically “in Houston”), she is repeating the grade.

The developing friendship between the two main protagonists is fascinating to behold. Kate is wily, but Olivia is more cunning than she appears, and the intricate dance the girls engage in while sussing each other out provides the reader with a clear glimpse into their characters.

Once their relationship is established, Toten throws the cat among the pigeons in the form of Mark Redkin, a new member of the school’s administration, whom everyone seems instantly charmed by. Everyone, that is, except Kate, who senses in Redkin a threat she can’t quite pin down. As Redkin and Olivia become involved romantically and he begins to exert abusive control over her, Kate is torn between self-preservation and a need to save the girl she has come to care for, despite her best efforts to remain detached.

There are a few key factors in the success of Beware That Girl. The first – and most vital for any good thriller – is that the reader is kept guessing. Just when we think we’ve got it all figured out, from the characters and their motivations to what’s going to happen next, Toten throws a well-timed curveball. These are often subtle enough that we only realize what’s happened after the next one has whizzed by. The pacing is also impeccable. What feels like a somewhat slow middle section turns out to be the perfect set-up for the last few chapters, building to a conclusion that leaves the reader a bit breathless.

Then there are the girls. Using first-person narration for chapters from Kate’s point of view and close third-person for those focusing on Olivia is a clever tactic that has the effect of making the reader think we know who is in control. By the end, however, we’re not so sure.

Backstories with just enough detail result in sympathetic, multi-layered characters we can’t help but like, which makes Kate and Olivia’s predicament much more intensely felt. While the secondary characters (including Olivia’s Polish housekeeper and guilt-ridden, largely absent lawyer father) teeter on the edge of cliché, they add necessary lightness and relief from the drama and intrigue.

Beware That Girl has all the makings of a crossover hit. It’s smart, dark, entertaining, and unpredictable. While comparisons to recent thrillers such as Gone Girl and Reconstructing Amelia are inevitable, the stealthy, expertly executed story is more in line with A.S.A. Harrison’s The Silent Wife, and that’s high praise, indeed.