> An investigation is a sequence of actions that focus on the process of discovery. As the investigation progresses, your character will discover clues and ask questions in hopes of finding out more information about the situation in front of them.
Leading to the truth is a set of clues: sign-posts lead to information, and that information leads to the truth. You can think of it like a tree: the root of the tree is the truth, and it splits off into branches that end at leaves. The characters start with the leaves of the mystery. From there they follow the branches back to the source.