My 2¢ after reading Egri: A theme which tells the reader a rule of the world.
Not a story: The king died then the queen died.
Is a story: ... then the queen died of grief.
The theme: grief overpowers life.
We look for themes as creatures who learn. This lesson: grief is powerful. Other lessons: be true to yourself, love conquers all, family is where you find it, real treasure is the friends... etc