When Sirius died Remus disappeared. Not forever, of course, and not even for long.
It was only a week, hours passing languidly through his grief.
He'd held up well until they got back to 12 Grimmauld Place and Harry was courted away to Hogwarts.
He'd gone up to the master bedroom, slowly, because he'd thought the hardest part would be telling Buckbeak.
That turned out to be his easiest task. Buckbeak knew, the moment Remus entered the room. Remus saw him find out. He'd choked up, for the first time that night, and stumbled over to the feather-strewn bed, reaching for a bedpost but finding Sirius's old nightshirt tossed atop it.
Remus had dropped it instantly, and then it hit him and he crumpled.
The first day Remus stayed on the floor, and there was no sense of time. He relived their first year at Hogwarts, the first time he'd seen Sirius, James, and Peter.
The second day Buckbeak nudged him up to the bed and their school years flipped past his eyelids, spinning and whirling and ripping his heart into pieces.
The third day he saw them graduate, four hand in hand, Sirius jumping on Remus from behind and cheering as the hats rocketed through the air.
The fourth day he saw Sirius's shock when James announced his engagement, sixteen seconds of gaping disbelief until the laughter and applause erupted. He saw Sirius's devious smile, the one planning to lace the wedding punch with firewhiskey eight months before the ceremony.
The fifth day Moody came to tell Remus that his condition prevented him from becoming an Auror alongside James and Sirius. He saw Sirius's anger, the dark passion flaring up from the depths of his being and roaring out through his eyes, his hair wild and soul thundering.
The sixth day he saw Harry's christening, saw Sirius hold his godson for the first time. He saw Sirius's love, the tenderness and devotion nearly stamped out in him from birth, that had persevered through his family's abuse but was cloaked beneath his lively, comical façade.
The seventh day Remus found out that Sirius had escaped from Azkaban, the newspaper falling to the floor, his teacup shattering, falling to his knees among the shards and retching. Twelve years-innocence-guilt-friendship-betrayal-Sirius and Remus howled in pain.
At the end of the seventh day Dumbledore opened the door and Remus remembered who he was. Dumbledore's cold hands lifted him off the bed and handed him Kreacher.
On the eighth day there was a new plaque on the wall of house-elves.