I have a gift. I am a smart person. Very few things get past me. I find it amazingly easy to see some thing and remember it. A look, a reaction, a sentence, a specific tone of voice. Whatever it is. I most probably will not understand it fully on the day, but my brain stores it away.
Time moves on and other things are noticed, and they become more complicated, like, what someone isn't saying, or is avoiding on purpose.
And my brain connects all these things done by the same person, or the same group of people and connects them in a way, if had to be done consciously, would be completely imposible.
A suspision, or guess is formed.
So using subtle methods, I keep speaking to the people concerned and comfirm that, yes they are indeed avoiding that subject, name, date...whatever.
The suspicion grows, until confirmation is reached.
It is a gift if someone is hiding something to harm you. But if someone is keeping something to protect you...
...it's a curse.