Ideas...

Schizophrenic protagonist has been talking to what is assumed to be a therapist, (as an older man?), but he isn't actually talking to anyone (audience doesn't know this yet). He has a friend who is in fact his hallucination, that helps him cope with the frustrations of having the mental illness. He enjoys playing chess with this character, as it settles the voices in his head. The therapist that he has been talking to seen, as no-one... It is actually the friend he has been playing chess with, showing that his hallucination acts as his therapist through-out his life.

Shot ideas?

Talking to a therapist as an older man ---> Goes for a lonely jog in a field in the morning ---> Close up of his face, he is talking to someone beside him ---> Long-shot to show his loneliness ---> When home, puts the kettle on, focusing on his hands ---> Steam fills the window, and he starts drawing shapes/lines (his visual hallucinations) ---> Sits down with cup of tea ---> Starts hearing voices, puts hands over his head ---> Makes his move on the chessboard ---> Showing his hallucination's hand make their move on the chessboard, eventually showing their face ---> Protagonist is calmer ---> The next day.... (MORE CONTENT HERE) ---> ENDING: He is older again, same shot as start of film, camera pans down to hands where he makes his move on the chessboard ---> Camera shows his opponent, there is no-one there ---> Shows him smiling.