You make the choice to switch the track to the group of four. What a monster, how could you do such a thing. Playing with lives is terrible and- oh it seems that those weren't people but eldritch horrors now pancaked by a train. Good Job, I suppose. Don't do it again.
You untie the remaining indiviual and he thanks you for your help. It turns out that he is a wealthy business man who was tricked by his rival, he offers to reward you for your bravery and quick-wittedness in deducing that the four over there were monsters. How clever of you.
Return to the fork?