Carl Walker, 35, is a man whose heart is buried beneath layers of caustic wit and earned cynicism. He sacrificed everything for the one person who mattered, and he paid the price by being cut off from his wealthy family. Now a physician’s assistant on the frontier of Mars, Carl’s only defense against the world is his spectacular ability to insult anyone who crosses his path.

Ezra Nolan is his antithesis: relentlessly sunny, quick-witted, and a dozen years his junior. An ambitious former heavy machine operator, Ezra crashes into Carl’s life with a request Carl can't refuse–mentor him through his nursing training. But Ezra doesn’t shrink from Carl’s venom; he tosses insults right back, confusing the veteran PA and slowly chipping away at his defenses.

Their attraction is electric, hidden beneath layers of professional protocol and biting snark. Carl is convinced he's too old, too damaged, and too much Ezra's superior to ever cross that line. Does Ezra's easy optimism conceal a deeper pain, and is Carl prepared to admit he wants the one person who sees past his fortress?