MC is a contractor hired by the city to demolish an old house that has been abandoned for over 50 yrs and recently condemned. During his initial walkthrough, he discovers an old diary. He pockets it to investigate later because something about it tickles his memory.
Upon his return home that evening he takes out the old diary and gently cleans it off. He is astonished to discover that it is identical to the one that he recently gave his young daughter. Opening it up, he sees the same message he printed on the blank first page prior to his giving it to his daughter. It also matches his handwriting.
He looks at the first entry and compares the handwriting to examples of his daughter's current handwriting and again its a match.
How? How had his daughter's diary ended up in a house that has been abandoned for the last 50 years? Quickly flipping through the diary, he sees that it is completely filled with entries. Going to his daughter's room and gently questioning her about the diary he gave her, he discovers that she has only made a couple of entries in it so far as she has decided to only make an entry about important events in her life.
So now the MC somehow has in his hands a way to glimpse into the future of his daughter, to help guide her in life. But that is scary... it would be too easy to go from helping her to manipulating her.