When Sirius Black died, something inside Tonks snapped. Emotionally it had left her unstable. It had been the event that proved to her that good didn't always triumph. Thus she lost her will to fight. She gave up; no longer did it matter who won or lost the great wizarding war. Pain was her enemy, her only enemy and all that mattered was getting away from it. The fight slowly left her and slowly she detached herself from the friends and life she had cherished.
Three months after the death, Dumbledore asked her to take a less active role in The Order due to her lack of any motivation. What mere months before would have killed her barely made a dent in her shell. The Order was no longer important in her life. Really, nothing was of any importance to her any longer. And so, without so much as a goodbye, she packed her things and left her temporary sanctuary in Hogwarts. She numbly walked into Hogsmeade and apparated to some random place from her memory. Tonks ceased to exist.
Her companions worried about her. They searched for her but with limited resources and a war being waged, it was only a matter of time before Tonks was forgotten. Tonks herself had long since forgotten what it was to enjoy life or to fight for what was right. She spent her time under the influence of whatever she came across. Life was now a hazy cloud full of ups and downs that Tonks rode merrily as a Muggle child might ride a merry-go-round.
Finally her mindless apparating landed her back in wizarding London. She spent days in the outskirts of Diagon Alley, not quite in Knockturn Alley but close enough, just leaning against a wall and drinking herself into oblivion. It had been weeks since she had cleaned her clothes or her body and even the other homeless Wizards were far more dignified than she. They refuse to come near her, adding more sorrow to the portrait painted by this now sallow creature.
But even the homeless wizards had cares. They worried about the war against Voldemort, about their lack of finances. Mostly, the war was on everybody's minds. They talked about what they had read in the Prophet everyday to keep their minds off their hunger. Tonks just sat leaning against her patch of wall drinking from her never-ending bottle, ignoring the talk.
Her mind had entered some dark place after Sirius had left; some horrible place devoid of life but also devoid of anything that could hurt her. She was safe there in her little world and more than content to destroy her body with chemicals and booze to help concrete her mind there. So far gone was she that she hardly noticed the sudden appearance of the dark figure. She spared no care for her wall mates who scattered quickly away. Nor did it matter to her when a wand was drawn and pointed at her.
What did matter was that finally, after a year of hiding in her corner of her mind, two simple words set her free. With those two uttered words, her mind soared up higher than any wizard had been on a broom before accompanied by a strange green light. But it did not matter to her. All that mattered was that life was suddenly grand and full of light and sound. She was free from pain, from guilt, from war. She was mended, whole, happy.
Tonks did not see the Death Eater apparate away with a smug grin upon his face. This had hardly been a trial for him. Defeating what had once been a powerful member of Dumbledore's own elite force against his master had been nothing more than a swish-and-flick. She did not see or care that his Master's mark marked the place of her body so high in the air. She was not there to witness the members of the Order that still survived apparating to her body and tenderly delivering her back to the old meeting place. She was blind to the tears they shed at her freshly dug grave. She did not see the flowers they placed upon her final resting place or the shaky hugs of reassurance in a time where none existed. The epitaph they left on her grave fell upon deaf ears, though it rang true in her heart:
What once was broken, now be whole.
What once was lost, now be found.
Be happy and finally free
