Nyota is not well. She is ... irritable. There are dark circles under her eyes and her usual vibrancy is missing. She mutters to herself as she works, finally jumping up and storming out of the office. In a few minutes she is back, unwrapping a chocolate bar. She sits at her desk and begins to work again, nibbling on the chocolate. After a while she calms down and concentrates better.

Spock observes. He has seen this behavior before. He recalls prior instances, analyzing all the data. There is some cyclical reoccurrence --- ahh.

Exactly 29 days later when Nyota drags into the office with cramps, there is a small box of chocolates sitting on her desk.