Single-setting thrillers are kind of my jam. They're cheap to make and often end up being some of the most entertaining movies because they demand a strong script to carry them. 'Old Man' didn't quite work for me sadly. There was an idea here that could've been pulled off if executed differently.
The main problem stems from the characters. There are only really two of them of note in the film. One is characterless because of the way he is set up. He adds some mystery to the proceedings but otherwise he is just clueless and going along for the ride. The other character is a crazy old man who rambles on about nothing for minutes on end. Those two don't equal a particularly enjoyable 97 minutes of viewing.
The thing the film has going for it is the intrigue over what exactly is going on. There were a few routes the film could've gone down at the end, so if anyone is saying this one is predictable I would take umbrage with that. Unfortunately though the whole experience is very forgettable and not one I'd recommend. 5.5/10.