You can find the person who went missing trapped in a cave and rescue them, and they return to the village. You can also have them as a follower and marry them.
It's all very buggy though. There appears to be no dialogue at all between them and the others there when they return, and there also appears to be no quest to find him (I have no idea if that is intentional or not)
Also once you marry them they continue going to Darkwater crossing daily, even if they are supposed to be living with you (Just annoying)
I have no idea what this cart is though. Was anything in it?