I've been planning a story that follows two characters. At the end, one character (let's call him Joe) goes back in time and appears at the start of the book.
I intend to explore themes of determinism vs free will throughout the story.
On the first read-through of the story, the reader does not know that the character who appeared at the beginning is Joe. Instead, Older-Joe is treated as a minor character and does not appear often.
I intend to follow Older-Joe's story: how he tries to use his free will to change time, and slowly realises that he cannot since the events have already happened. He eventually realises that he is not truly in control of anything, since he knows his own future and has no power to control it in any way.
I would like to mislead the reader into thinking that the book tells the story of Young-Joe. Upon reading the story for a second time, the reader would pick up some form of clue that indicates that Old-Joe is Young-Joe from the end of the book. Using this knowledge, the reader would then notice details that point towards a second story detailing Old-Joe's mental struggles.
How can I make these small pieces of information seem unimportant on the first readthrough, but incredibly relevant on the second readthrough?
Ideally, they would need to be completely forgotten, but carry some sort of relevance to an event or object at the end of the book in order to link Old-Joe to Young-Joe.