As Anglo-American leaders gather to plan the defeat of Nazi Germany, Hitler orders the death of President Franklin Roosevelt to derail the conference. Brandon Armitage, a Canadian veteran of the Great War, has joined Canada's Volunteer Guard to oversee German prisoners; it's a role he's undertaken to seek revenge for the death of his son during a raid on the French Coast. When one of his prisoners escapes.

Armitage pursues him to a remote island above Lake Huron, where FDR is on a pre-conference fishing trip. Suspecting the German is trying to assassinate the American leader, Armitage alerts security officials. When they refuse his help, insisting their security is tight, Armitage must act alone, even as he seeks to rescue his failing marriage.

The Quadrant Conspiracy is based on an actual historical incident and is set against the backdrop of the Allied march to defeat the Third Reich. While there are elements of a thriller, the story also centers on the effect of two worldwide conflicts on a marriage.