Cassian has a cold, and he wants to sleep it off on top of Jyn. He follows her around all day, just leaning against her or resting his head on her shoulder or wanting to hold her hand. Eventually, they decide that no work is getting done today, so they might as well go back to bed.

(I know it's probably OOC, but my heart longs to hear Jyn call Cassian a pet name when they're alone together, so, bonus?)