In this novel, a young sleuth participates in a mystery marathon that feels like a game of Clue, inviting readers to test their skills.

A mysterious package arrives that invites college student Sara Donovan to a gathering at a sumptuous country estate that offers megabucks to the winner of a contest. The nine participants must find and then figure out a series of clues, the victor being the first to do so. For help, Sara has her math genius brother, Matt; her faithful dachshund, Mauzzy; and her best friend, the spirited Zoe Harp. Readers also meet Sara’s boss in her side job as an office/research assistant, Melvin “Finn” Finnegan, a private investigator who is a lot smarter than he lets on, and the very mysterious Sadie Majelski, whose guise as a twinkly older woman hides formidable talents and secrets. Game on. Some participants drop out and at least one is murdered, but Sara and Zoe doggedly press on, cracking both safes and the enigmatic messages they find inside. They finally suss out who is behind the whole thing, an evil genius who is jealous of Sara’s growing reputation. But the mastermind gives the cops the slip and will remain a lethal adversary. Keep in mind that this is the third installment of a mystery series, so up pops Majelski at the end to hint at unfinished business. Polcari is clearly having a ball here, in what is in most ways typical fare: the likable, if frazzled, hero; her smart-mouthed but loyal sidekick; and the nerdy math whiz for backup. The author is a lively writer, as when, after a stressful weekend, Sara rejoices that “Monday finally got off its butt and decided to show up.” There are lots of unnerving, shady characters to speculate about, even better than Colonel Mustard, Professor Plum, and their cohorts. But there is a busyness to the plot (it just keeps shoveling in more clues and twists) that can be overwhelming. The puzzling out of the clues can sometimes seem overdrawn and repetitive, at least for those not into numerology games. But for those who are, this will be grand fun.

An enjoyable, complexly plotted series installment that promises more mysteries and thrills to come.