Barty, my love.

If you're reading this, it's too late. I've failed.
I've failed you, I've failed my brother, I've failed myself.
I was meant to come back. We were meant to face the Order and seek asylum together. Maybe you would've been able to see Sirius as he truly was then. I think you two could've been great friends.

I know what you're thinking. If you want to blame anyone blame Voldemort. He was the only reason I had to take on this task and fail it.

I'm going to miss those nights that we were able to get away and just be us, just hold each other, just forget that there's a madman threatening to shatter our sanity and destroy our humanity. I'll miss your kisses, your touch, your warmth, your laugh, your thoughts, the way you would just hold me, for hours on end, and I'd wake up to see that you hadn't slept, the way you could promise that everything will be alright and I could believe it. I don't ever want you to think that you broke a promise to me. Years down the line you'll find you were telling me the truth, love. It just took longer than the both of us thought.

I wish we could've been more open about what we had, and if I had succeeded, we could've. Sirius and Remus were. And they were just fine. None of that homophobic crap the other Death Eaters sprout that forces us to stay silent about our feelings around them.
I wish we could have had longer.
I wish we could've seen the end of the war together.

I can't stop you from trying to find me, I know that. So I want you to promise me some things.
Promise me you'll go to the Order. Take this letter with you. It's been spelled not to show anything about you and I just in case. That's your decision to make, not mine.
Promise me you'll try to get to know my brother and his friends? I understand that my brother can be pigheaded, but his friends aren't as bad. You need someone to keep you sane now that I'm gone. If this letter doesn't already break you.
Promise me that if by any chance you happen upon my body - I pray you don't go anywhere near where I was, but if you're resilient enough to find a way - promise me that you will try to have me buried in a place where both you and my brother will both be able to visit, and might possibly be buried next to me, either side, when the time comes.
Most of all though I want you to promise me that if you find someone else, you'll take the chance. I want you to be as happy as you can. Don't dwell on me when there could be someone else who will try to love you just as much.

I love you, with all my heart. Don't ever forget how amazing you are. Be safe, and make the right decision. Do the right thing, for me.

I will wait for you.

Your friend, your lover, your protector,

Regulus Arcturus Black.

Barty finished reading the letter with a great heaving sob, already feeling the ache in his heart, and the fractures in his mind. It was too late, and he didn't know if he could make any of those promises.
With his tears slightly blurring the parchment, and his weight leaving a dull throb in his knees - when did my legs give out? - Barty was torn. The pain was far worse than any he felt Voldemort could ever attempt to inflict upon anyone on the earth, and all he wanted was to make someone else feel it.
This wasn't fair. None of it was fair. The war, the prejudices, the loss of his soulmate. It was all just so unfair that Barty just wanted to lose control, and obliterate something. Anything. With Voldemort he could do this. But siding with Voldemort may very well mean that he'd just break his better half's heart again on the other side.

Pulling out a piece of parchment and some ink, Barty vowed to do what he could to fulfill Regulus' wishes. And he started by writing to the Order, and getting some sleep, however restless it was bound to be.