Disclaimer: HP not mine.
Beta'd by the loverly dress-without-sleeves. And what's so wrong with a dress that has sleeves, anyway? Is this sleeve discrimination? (Btw, she's got an awesome Mrs. Black fic. Go read, yo.)
You think you are free, but you aren't. Freedom is a choice and life is a cage, and consequences are inescapable.
You know that you are better than your brother, better than that traitorous Gryffindor who dishonors the Black name by associating with Mudbloods and half-breeds, and you want everyone to know it.
You enter your cage blindly, poison-sweet promises filling your ears.
You bow and kneel of your own free will, groveling like a common servant before a crimson-eyed murderer, and the knowledge that you chose this, that you've come to Voldemort freely, stings like a thousand lashes against your soul, staining you red and leaving you broken.
For a while you can still fool yourself into thinking Voldemort is something other than a madman, something better than a criminal, but you are wrong.
You realize you are trapped, and will be a prisoner until the day you die. You realize you've sunk to depths nobody can lift you from. And you realize that if you want freedom, you'll have to sacrifice something for it; if you want to be Sirius' equal, then perhaps you'll have to be his equal in anonymity.
You choose to drink the poison and steal the amulet, leaving a fake in its place. You leave a note as well, the message gloating, because you've chosen freedom and you are dead anyway. You hide the amulet away and, weakened by the poison but strengthened by your convictions and choices, you defy the Dark Lord. You announce to everyone that Voldemort is a killer and nothing more, that he is unworthy of fear or respect.
You see a flash of green light, and know that you are free.