Do I look like a maniac who goes around killing girls?

Virus/The Brain That Wouldn't Die/Diary of a Nudist (1980/1962/1961)

Triple Bill of Public Domain movies.

Virus was not the film I thought it was going to be. For good and bad. Starting with a silhouette of a lone dishevelled figure framed by the sun, it felt like it was going to be a post apocalyptic movie ala Mad Max 2 and the pulpy opening bore that feeling out. But it shifted into a politically minded take on how the end of the world might go down (though a terribly simplistic version, I liked Glenn Ford and Robert Vaughn as upstanding politicians - the military are the villains here).
It then shifts again to focus on a handful of the last 800 people presumed alive, and dodgy sexual politics (1 woman per 100 causes an interesting discussion that seems settled far too quickly) and science aside manages to be an unusual take on the disaster film format popular in the 1970s (this has a big name international cast).

The Brain that Wouldn't Die is mostly a cool hook looking for a movie but has some unsettling ideas (it opens on blackness with just a female voice asking to "let me die, please let me die".

Diary of a Nudist is just terrible. A dull, badly filmed attempt to titillate. About as sexy as a dung beetle. But a curious time capsule and features (possibly originated? - i'm not too up on the naturist oeuvre I'm afraid) the great naked volleyball cliche.