Describe the only time Michael sees Hanna by chance, in Chapter 16.

Hanna has been behaving oddly for days, and when Michael questions her behavior, she snaps at him. It is a hot summer's day, and instead of reading, all Hanna wanted to do was bathe Michael. Hanna and Michael then made love, and Hanna tells Michael to go to his friends. Michael leaves and goes to the pool, where he meets friends. By chance, Michael looks up, and sees Hanna nearly 30 meters away, dressed in shorts and a blouse knotted at the waist. Because of the distance, Michael cannot see her expression. Michael takes his eyes off Hanna, and in that moment, Hanna was gone.