If you can stomach the acting of any given LIFETIME movie, you can handle this movie.
It may not be what you were expecting based on the description, but if you stick with it, it gets better & better. If you go into this faux-documentary thinking "Missing 411", you're more equipt for the eventual storyline. And if you've never heard of the "Missing 411" stories, check them out. They're unsolved mysteries of people suddenly going missing, with clues of what happened to them that never seem to add up. Sometimes people are found alive weeks later with no memory of having been gone for vast amounts of time, some are found dead, and some are never found.
I think what turns viewers away from this movie is that it's bringing in the wrong crowd. Most start watching this for the documentary aspect of a crime/mystery/thriller and their expectations are poorly met. But if this was marketed towards supernatural, unexplained mysteries, "Missing 411" type of genre, it would fare far better with the viewing audience.
You wouldn't label a "Romantic" movie a "Thriller". Generally, women like romance and men like thrillers. What would you expect when you lure the wrong audience in for a thriller and they're stuck watching a romance? Very bad reviews and a low rating. Imo, that's what's happening with this movie, "Howard's Mill".
If you like the "Missing 411" series, supernatural phenomenon, and unsolved mysteries, then this movie is for you. And I'm pretty sure you'll enjoy it too.