They agreed on one rule: no labels.
Nova Reyes doesn't do relationships anymore. Not after watching herself disappear into the last one. Marcus Bellamy doesn't do commitment, period, not after watching his parents' marriage curdle over twenty years into something neither of them recognized. So when a one-time thing turns into a running arrangement, they draw a clean line: no boyfriend, no girlfriend, no promises.
Just don't touch anyone else. And don't ask why that rule matters more than either of them wants to admit.
It should be simple. It isn't. Not when he shows up every night without being asked, not when she's the only person who's ever made him want to stay, not when the mere sight of someone else's hand on either of them sends something fierce and unreasonable through the both of them; jealousy neither can explain without admitting the thing they swore they wouldn't feel.
As the lines they drew start blurring past recognition, Nova and Marcus are forced to face the truth: you can call it whatever you want. Doesn't mean it isn't already everything.