(As always, this isn't a key, just an angle to observe)

I'm sure this has been discussed before, but the piece of the Pandora's Box analogy I wanted to mention might not have --

After opening Pandora's Box and releasing all the evils into the world, the only spirit that they manage to keep in the box was Hope.

The old people in the beginning are around as Betty shows up full of hope.

The old people at the end finally escape the blue box, as Diane gives up hope and is driven to her to suicide.

Nice observation.