Nova Scotia, 1916. Angus MacGrath, a skilled sailor and navigator, is lost—caught between a remote wife, a disapproving father, and a son seeking guidance. An ocean away from his coastal village, missing is Ebbin Hant, Angus's adventurous brother-in-law and best friend. Ebbin's unknown fate sets angus on an uncharted course with profound consequences for those he loves and those he comes to love.

In search of his own purpose and hoping against all odds to find Ebbin, Angus defies his pacifist upbringing and enlists. Assured a safe job as a military cartographer in London, he is instead assigned to the infantry and sent to the blood-soaked mud of the front-line trenches in France, where he begins his search.