Disclaimer: JKR owns everything.
It was very quiet. Too quiet, in Minerva McGonagall's opinion. The air had been filled with tension for several hours now, ever since Albus Dumbledore said he was leaving for a few hours. She didn't like it, and had been pacing in her quarters for a good twenty minutes. Where was Dumbledore? Furthermore, where was Harry Potter? She hadn't seen the boy all day, highly unusual for someone of Harry Potter's status and talent for trouble. Something did not fit into the equation, and the cool, calculating mind of Minerva McGonagall was ill at ease.
Her pacing was brought to a halt by a tapping sound on her window. She stopped walking and could only stare. The tapping continued, louder, and she came to her senses. She crossed the room with three long strides and opened the window, and a rush of red and gold feathers came inside.
"Fawkes?" she said incredulously.
In his beak, the phoenix carried a piece of parchment, which he let fall. He looked at her for a long moment, then vanished in a burst of flame.
Minerva was puzzled by the bird's actions, but her mind quickly turned to other things when she saw what was written on the outside of the parchment.
Her name.
In Albus Dumbledore's handwriting.
She gasped and dropped to her knees, forgetting all about Fawkes's sudden appearance. A letter from Dumbledore? What could it mean? Some explanation, perhaps? There was only one way to find out.
She unfolded it and began to read.
My dear Minerva,
I am afraid that if you are reading this, it means one of two things: that my hours are numbered, or that I am already dead.
I don't know how you received this letter. You may have found it while cleaning out my office, or it may have been brought to you by Fawkes, who watched me write it and gave me a rather disgruntled look when I told him I had to intent to send it. At any rate, it has somehow found its way into your hands.
There are so many things I wish I could have told you. Undoubtedly your mind is full of questions, questions I am no longer able to answer and no one else knows. Generally speaking, foresight is blind, but hindsight is perfect. I must say that though the hindsight holds true for me, the foresight was only clouded. I do not regret withholding the information that will undoubtedly lead to my demise; please understand that it was only to prevent further loss of life, and I had I told you, I would certainly regret it. All I can tell you is that there is a traitor in our midst and actions must be taken that may never be understood. What I do regret, however, is that I waited until now to tell you what I am trying very hard to work up the courage to write.
I have told you many times that I respected you, admired you, needed you. I do not think, however, that you had any idea how much I needed you. I remember the day I fell in love with you. It was May twenty-first, nineteen sixty-eight. It was a Saturday. It was the last Hogsmeade weekend of the year, and as you were walking out of the castle with the students, you looked back and smiled at me. That moment, that smile, unleashed a whole new set of emotions that I could not comprehend and feared I wouldn't be able to keep concealed. I have cared about other women in my life, but none of them the years and intensity that I have loved you.
Perhaps if I had told you this long ago, things would have been different. Perhaps I was afraid that if I told you how I truly felt, I would have lost the amazing friend I had in you. It is remarkable how one can be deemed so courageous in some aspects of life, and yet remain a coward in others. It is too late now, I'm afraid, but I could not let this knowledge die with me.
This is for all the times I didn't tell you what was in my heart.
This is for all the memories we never had the chance to make. This is for all the times I should have said I love you and didn't.
I am saying it now. I love you, Minerva McGonagall. The only regret I have in this life with regards to you is that I found the courage to tell you of my love when it was too late. I swear to you, though, that when we meet in the next, and every life after that, I will not let you go. In the meantime, please promise my memory that you will ensure that others do not meet our fate. It would make me happier than anybody to know that there was a little more love in the world.
And with this, I bid farewell to you, the almost love of my life.
Albus P. W. B. Dumbledore
Minerva could not breathe by the end of the letter. She was sweating, and her hands were shaking. This couldn't be true. He could not be dead. Not Dumbledore, the man whom she'd secretly loved since the same moment he confessed he loved her. It was impossible.
Then, a great noise interrupted her thoughts: banging and shouts, coming from all directions. Hogwarts was under attack! She dropped the letter and rushed outside, wand at the ready. Sure enough, the corridors were darkened with smoke and the presence of evil. Some great evil was at work inside these walls… and it was their duty to stop it.
Minerva began running, and soon saw a familiar shape in the darkness. "Filius!" she cried upon recognition of the small man's form. "What's going on?"
"Death Eaters!" tiny Professor Flitwick exclaimed. "Death Eaters are inside the castle!"
"We must stop them!" said Minerva. "Dumbledore must be here – find Severus immediately! We will need his help… Hurry, there isn't much time!"