They looked at each other, with a certain degree of suspicion at first. Neither had expected the other to be there. You know how it goes. One minute you’re walking along minding your own business when bang, it happens.
Sometimes it literally does happen with a bang and you bump into each other. In Stella’s case it was metaphoric bang. She had just been ambling along with her mind somewhere else and had stopped by the river bank. There might have been something that had caught her eye but then again there might not.