Matthew Scudder (Liam Neeson, sporting a not entirely convincing American accent) is an alcoholic ex-policeman turned private detective. He's approached by a fellow AA member (Boyd Holbrook), who wants him to help his dealer brother (Dan Stevens) whose wife was kidnapped, the ransom paid ... and the wife is gone, presumed dead. It becomes clear that this isn't a single crime, and that the kidnappers are targeting drug dealers.
Wikipedia refers to this as a "neo-noir," which seems pretty accurate. The kidnappers are a modern evil - completely free of conscience, they dismember people slowly for fun. While I thought David Harbour and Adam David Thompson sold these two horrible creatures fairly well, I thought it was one of the weaker points of the movie to sell them as totally not human. But the weakest part was the bizarre and not very convincing friendship Scudder develops with a 13 year old street kid (Brian Bradley), who's fairly smart but also predictably gets into trouble. Not a bad movie, but violent and very nasty without a great deal of reward.