In 1943 a strange and daring plot unfolded in Canada, one that sounds like the script of a wartime thriller. Four of Germany’s most celebrated U-boat commanders, including Otto Kretschmer, the infamous “Tonnage King,” were being held at Camp 30 in Bowmanville, Ontario. Behind the fences they hatched an audacious escape plan. They would dig tunnels, slip across Canada, and meet a German submarine waiting on the coast of New Brunswick. The plan was called Operation Kiebitz, and it had the full backing of Admiral Karl Dönitz himself.

But what the prisoners never knew was that Canadian intelligence had been watching the entire time. Every coded letter, every smuggled map, every shovelful of dirt was being tracked. When the breakout came, the Canadians had their own counterplot ready, Operation Pointe Maisonnette. It was a contest of patience, deception, and nerve, and in the end it would be the Canadians who had the last word.