Pretty Poison (1968)

Pretty Poison (1968), directed by Noel Black.

For years, Anthony Perkins has been institutionalized for teenaged arson and (accidental) murder. Now he's out and pursuing his avocation as secret agent and industrial saboteur. High school senior Tuesday Weld (age 25) joins in and it's youthful fantasy rebellion (with a bit of real sex and fake drugs) vs the stodgy straight world of mothers and polluting factories.

That part is a mildly quirky comedy, but it turns darker when on one of their "missions" Weld kills a night watchman. It seems easy and natural for her and we realize Perkins is not the crazy one. They plan a getaway but he knows it will be a quick slide to doom.

The turnabout at midway is the big plot development: Perkins is initially in charge but then becomes an adjunct to her craziness. He asserts a moral compass at the end, not that it does him much good. We never know if she gets away with it.

Filmed in small town Massachusetts.