Prodigal

He nearly destroyed the world, but with her help, he can save it.

Adam Alsing—at least that's what they tell him his name is—has no idea who he is or why he's huddled naked in the snow next to a mysterious silver pod. When a gorgeous, no-nonsense sheriff by the name of Claire Lawson rescues him, she explains the planet's under attack—and he's been missing for over two years. The problem is, what he doesn't remember can kill them.

Keeping the peace in her post-apocalyptic town is all the trouble Sheriff Claire Lawson can handle. Until the MIA Chosen One—the guy who could have prevented the apocalypse—interrupts her supply run. The Shipborn aliens want to study him, and what's left of the Terran government wants to lock him up. But his charming demeanor and his desire to help, along with his sexy smile, has Claire fighting her better judgment to keep Adam around. For now.

But can she afford to feel such sympathy and desire for Adam when an unknown evil begins stalking her town as if being coordinated by the only newcomer--Adam himself? 

Tropes: This "amnesia during the apocalypse" romance includes a hard-ass alpha female, some law enforcement, and a redemption arc.

Maelstrom Trilogy:

1. Angeli

2. Traitor

3. Prodigal