Shattered Oath by Em Petrova

He’s the ghost in every system. She’s the rogue asset the government erased. The only place they’re real is in each other’s arms.

Special Operative Caius “Sinner” Sinclair has always been the butt of a running joke on SEAL Team Blackout Charlie—what exactly does Sinner do? But when command drops a new mission in his hands, the past he’s never shared is about to crack wide open. He’s ordered to lure in the terrorist Cipher…with a partner who guards her secrets as fiercely as he does. The same one who makes it harder every day to keep his hands to himself.

Opal Simmons has lived too long as the FBI’s perfect pawn used as a weapon that gets results. She might not have a choice in the op, but she calls the shots everywhere else. She knows exactly how dangerous it is to show weakness, especially to a man like Sinner who sees too much already—and awakens a hunger for his touch and his kiss she’s terrified to feel but can’t push away.

As the op turns darker and deadlier, trust becomes the one thing they can’t avoid—and the pull between them the one thing they can’t deny. Falling for each other might wreck the mission…but losing each other would be far worse.