It’s 1942 and after a sexual indiscretion, US Navy pilot Zachary MacKenzie is sent to serve in the Royal Navy’s submarine service—a shockingly harsh punishment for a man who loves to fly. The submarine is oppressive and frustrating for him, and he’s marked out from his peers, publicly by being American, and privately by his attraction to men.

The only bright spot is the company of his steward, sonar operator Gethin Llewelyn. Despite the differences of rank and background, they’re drawn to each other. Gethin’s integrity complements Zach’s casual joie de vivre, and soon the friendship develops into something much more.

As the threats of war increase, the submarine is plagued by potentially hostile vessels, and circumstances lead them to suspect there’s a spy amongst their own crew. Being forced even closer together as they work for the greater good reveals a new awareness, and Zach doesn’t know what is in more danger, the vessel under his charge or his heart.