It had started a few weeks ago. Subtle. So subtle Isadora had nearly convinced herself it hadn’t happened at all.

Her family was flying out for a weekend vacation—the kind her father insisted on when business deals needed smoothing over and her mother needed something to post about. The driveway was packed with luggage and noise. Her brother was on the phone arguing with someone, her mother was already sighing about the late flight, and the help buzzed around, trying not to get in the way.

And then there was Marcus. Quiet. Efficient. Always composed.

He moved like he was born in a pressed uniform—stoic, strong, and unbothered by the...