The popular code-cracking teenage spy returns for another adventure, this one involving poisonous snakes, traitors, and vicious rumors. Ruby adds martial arts and the ability to see in four dimensions to her skill set, but otherwise the series formula is the same: expect suspense, witty dialogue, and intriguing puzzles, along with occasional uneven pacing and rambling moments.

In the series' penultimate adventure, the whip-smart, code-cracking teen spy for the secret Spectrum agency takes on venomous snakes, traitors, and evildoers but is helpless against poisonous rumors circulating at school.Out of loyalty, Ruby took the rap for classmates whose fight summoned the cops; now she's grounded, sentenced to community service, and forced to babysit Archie Lemon, age 1. After solving many cases for Spectrum, she's suddenly frozen out of important briefings; do they think she's the suspected mole? Her quick action saves a querulous neighbor's snake-bitten dog but nets her only his abuse. No good deed goes unpunished, but the white 13-year-old isn't about to give up sleuthing. There's something weird about billboards advertising a new soft drink; investigating leads Ruby to familiar foes. Set in 1972 Southern California, the series, by an English author, has a 1950s sensibility (typical exclamations and epithets include "jeepers" and "Sam Hill"). The cellphone- and computer-free cultural ambiance is refreshing, but although the once-cartoonish characters have deepened over the series, their largely all-white world hasn't evolved. It's Little Lulu and Archie territory—no Vietnam War or cultural upheaval here. However dated, the ingenious puzzles and humor, especially in dialogue among Ruby and her peers, remain highlights. Still, slow pacing, frequent digressions, and unsentimental, bone-dry humor may challenge U.S. readers used to nonstop action and a straight plot throughline. Rewards await persistent readers: sly satire, quirky detail, and a smart, opinionated heroine brimming with ebullient self-esteem. (afterword) (Mystery. 9-14)

In a sense, there's nothing new in this fifth title in Child's popular series: brilliant 13-year-old Ruby Redfort, Spectrum's youngest field agent, will once again use her code-cracking skills to find out what the dastardly count is up to and thwart his plans. In the process, she'll receive martial-arts training, trade witticisms, and dispense fascinating facts about poisonous reptiles and other seemingly random subjects. Child provides something rare and wonderful in middle-school fiction: the refusal to dumb down content, offering young readers a long book with multiple opportunities to learn something new (in this case, how to see in four dimensions). Long live Ruby Redfort!