Matt Scudder (Liam Neeson) is an ex-NYPD cop who now works as an unlicensed private investigator operating just outside the law. When Scudder reluctantly agrees to help a heroin trafficker (Dan Stevens) hunt down the men who kidnapped and then brutally murdered his wife, the PI learns that this is not the first time these men have committed this sort of twisted crime nor will it be the last.