All of the secrets and getting to the bottom of something provide motivation for the characters to perform certain actions or to behave in a certain way. For example, when Harry hears the voice of the Basilisk in the walls, or when Hermione's petrification gives them a clue as to what the Basilisk is, the characters in the book don't just stop trying to figure things out, they continue to act in a manner as to find out the rest of the information and get to the bottom of the mystery. Another example comes when Harry finds out that Sirius is his godfather, and that he supposedly betrayed his parents to Voldemort. This acts as a catalyst for Harry to seek out Sirius and that lets the rest of the plot points in the book occur.
This motif has connections to several characters throughout the series. One of the characters that the secrets and truths have a major connection to is obviously Harry. Harry Potter can be connected to just about any aspect of the stories. He is connected to the secrets and truths because most of the secrets are about him or have something to do with him or are important to his life in some way. The truths are generally revealed to him or are about him or are also important to his life in some