“Sometimes you’re working,” she pointed out, quite logically. Then she grinned up at him innocently.
“But that’s when I’m at my most fascinating,” he insisted. After a beat, he clarified, “Well, lab work. Desk work, not so much.”
“Nononono, I mean, when you are working, sometimes I /can’t/ see you.” After all, if she agreed with him on the fascinating bit, his ego would shove them both out of the room. “After all, I don’t go with you on business trips. You make wonderful faces at the desk work.”