We do know that its the Cold War 1950s.
Irina wants him to help find the skull because its the key to mind-controlling knowledge.
Anyhow, if Indy is a salty coot, the movie sticks to the old ways, too.

Credit: David James
That still leaves over 100 minutes to fill, though.
The skull may be transparent, but the plot is murky as hell.
Of course, theres no question whos going to win.
In this revival of the Indiana Jones franchise, everything is new and nothing is new.
The movies legacy may simply be the melee that ensues when Spielberg cracks the whip and moviegoers scurry for tickets.B-