Kiss Me Deadly was a 1955 film noir directed by Robert Aldrich (who later went on to direct Whatever Happened to Baby Jane?, Flight of the Phoenix, and The Dirty Dozen). It came at the very end of the original noir era. And it had by far one of the weirdest endings ever. (So this WILL have spoilers. Sorry!)
The main character is the archetypal film noir detective, Mike Hammer (Ralph Meeker). He's crude, he's misogynistic. He has a hot secretary, Velma, who is in love with him, but he doesn't care. He's Mike Hammer, dammit.
The film begins with Hammer driving down a country road one evening and encountering Christina (Cloris Leachman). She is the Mysterious Woman who sets Hammer off on the case and then dies.
The plot twists and turns like a roller coaster. There's Lily (Gaby Rodgers), who pretends to be Christina's roommate, but is actually after some sort of mysterious box (nicknamed, in a bit of genius, "the great whatshit" by Velma). The box is the archetypal Maguffin. It's only there to move the plot forward. Or is it?
Well, in this case, no, it isn't. There is a purpose for the box. And here there be BIG SPOILERS, so if you want to watch the movie without knowing what's going to happen, stop reading. The purpose of the box is this: it represents the end of the world.
That's right, ladies and gentlemen. See in the movie poster where it says "Latest H-Bomb!" They weren't be figurative: the box actually contains radioactive materials needed to built an atomic bomb. That's the Maguffin everyone is searching for. At one point, Mike Hammer opens the box and his hand gets burned by radiation - so we know, contrary to the filmmakers at the time, Hammer is almost certainly doomed.
And, even worse, is the ending. (Yes, I am going to spoil the end.) Velma is, of course, kidnapped and taken the evil villains house. Hammer goes there and gives up the box. The villain opens the box. The box explodes (in the original ending, Hammer and Velma escape; for the longest time, this ending was cut, so it is assumed that they both died). Since this is an atomic explosion, this pretty much dooms whatever city it took place in. And the surrounding areas.
There is a reason that critics have called this film "apocalyptic." Because it is. Because it takes the tropes of the normal film noir and it brings up the shadow of the Cold War and it smooshes them together and shows you exactly what would happened if they met. It showed you just how out of his depth the detective was, how dangerous the radioactive material was, how nothing anyone did mattered. This was the bleakest film noir until Chinatown.
And it is awesome. Sorry for spoiling so much, but you guys need to watch it.