What was up with that whacky prophetic vision of the Queen's? Let's take a closer look:
They say she saw our father beside her again,
Restored to life. He then took hold of the staff
He used to carry and now Aegisthus wields,
And planted it on the hearth. This sprouted up
And grew to a leafy branch which overshadowed
The whole of Mycenae. (418-22)
There are a couple of different ways that you can interpret this dream. The "staff" mentioned could symbolize Agamemnon's power, generally speaking. The old King might be physically gone, but the roots he once put down in Mycenae still have great influence and continue to sprout. On the other hand, the scepter could symbolize Orestes himself. Orestes, at first just a tiny harmless seedling, has grown up to be a threat of major proportions. And now he's back and overshadowing the Mycenae that Clytemnestra and Aegisthus govern. Regardless of the way in which you interpret this symbol, there's no denying that Agamemnon's presence is still felt.