The Dark Pictures Anthology: The Devil in Me

Mark must survive. Eventually he will traverse to a lighthouse during the ending scenes of the story. It is possible that there, he will be accompanied by one of them: Charlie/Kate
When he climbed that lighthouse, he may struggle to locate a generator. That one is not down in the basement like we possibly had expected. It is on top level. Up there, shimmy to his left once he has entered on its balcony up there. Power it up.
Return to that lighthouse's controls, and activate.
That lighthouse will get lit.