Impact shows great promise in its first half, when industrialist Brian Donleavy's wife (Helen Walker -- the psychologist in Nightmare Alley) gets up to some homicidal duplicity. It's hard-core noir all the way, especially when push comes to shove on a dangerous mountain road. But then Donleavy ends up in Larkspur, Idaho, apparently suffering from amnesia, and falls for a girl mechanic. From here on in the tone grows sentimental and "women's-picture"-ish. When the climax comes, everybody seems suddenly to start behaving like imbeciles. There's enjoyable moments in Impact, but it's too compromised to be vintage noir.