There was one thing you were amazing at, and that was reading people. When your parents were lawyers and always had a hard look on their face, you grown used to noticing the little things that gave way to what that person was thinking or feeling.
That's why your friends never lied to you and said, "I'm okay," when they truly weren't; that's why everyone always told you what you wanted to know – because it was better for them to just tell you, rather than you just stating it out loud, probably in public.
But River was the first person you couldn't read. It was evident that something was wrong with him, that he was in need of help, but you didn't know what. And that has bugging you ever since you saw his first message.
There was something fishy going on, and you were going to solve it.