Track 6: The Ground Beneath Her Feet (Aidan's song 1)
By: U2
Explanation: Okay, this should be one of the most obvious choices.  The whole song in general sounds like Aidan's situation with Ferio but I've italicized the lines that I think sound specifically like him.  Particularly the line "I won't rest until you're found", which you will see an example of in a few episodes soon...

All my life, I worshipped her
Her golden voice, her beauty's beat
How she made us feel, how she made me real
And the ground beneath her feet
And the ground beneath her feet
 
And now I can't be sure of anything
Black is white and cold is heat
For what I worshipped stole my love away
It was the ground beneath her feet
It was the ground beneath her feet
 
Go lightly down your darkened way
Go lightly underground
I'll be down there in another day
I won't rest until you're found
 
Let me love you, let me rescue you
Let me bring you where two roads meet
Oh come back above
Where there is only love
Only love...
 
Let me love you true, let me rescue you
Let me bring you to where two roads meet
 
Let me love you true, let me rescue you
Let me bring you to where two roads meet,