Wen Ning recognizes what is happening. He is being confessed to. This happens to him, sometimes. There is something about him that makes people tell him secrets, although he doesn't think he does anything to encourage this. His sister used to say he had trust-worthy proportions, which people could naturally see. Since she had never read his fate in his face, this doesn't seem too reliable.
Wen Ning encounters Lan Xichen, and they discuss trees. A secret is shared.
Thanks to twigofwillow for fic-doctoring and help with structure, and to @superborb on twitter for wrangling my punctuation and spelling.