Was Dustin not supposed to know that Tegan had rejected his approach?

Dustin’s affection was profound. He was unwilling to force an already married woman into a difficult situation or subject Tegan to societal scrutiny. He refrained from continuing his confession and simply watched her leave the office and step into the bright sunlight.

Dustin thought to himself that such a wonderful woman deserved to live in the sunshine. However, he couldn't help but be concerned for Tegan.

Every day, Nayel