Teenage brothers Jack and George are back in another Second World War spy thriller for young readers. In this one, the Canadian boys travel with their family to Britain and plunge back into a world of intrigue overseen by “Little Bill”, William Stephenson, while their code-breaker mother serves at Bletchley Park. As with previous novels in the series, history and action-packed fiction are well-balanced, from the start, where they escort a German naval Enigma machine to Bletchley to an ending of high-adrenaline drama with a German spy. Many historical figures cross their path; the author’s afterword expands a little on these people. Though the teens’ involvement is improbable, it doesn’t tax the bounds of imaginative plausibility. George’s first person narrative is able to explain unfamiliar things to younger readers without seeming to lecture. This would be a great read for teens and older children.