March 2, 1982
12 Grimmauld Place
It was well past little Harry's bedtime when the last of the partygoers left Grimmauld Place.
Sirius and Remus weren't concerned– it was only one night, a very special occasion at that, and chances were Harry would have been too wound up from the excitement of their custody hearing to fall asleep anyways.
Neither of them were worried about getting the little boy onto some type of schedule in the coming days– they were confident in the ready assistance of Pillowtop, Mopsy, and Isobel McGonagall.
Nor were they concerned about Harry's initial absolute lack of reaction to his new home. Little Harry had not, they summarized, spent nearly enough time in one place– it was abundantly clear he did not expect to get to stay. But the child psychology books Remus poured through every free second he had assured them that this apathy was normal, and that over time Harry would relax into the stability and routine they provided.
But the remaining Marauders did have one increasingly problematic concern, and there was a dark cloud hovering over the pair as they laughed and smiled and passed around cake to their guests.
Sirius' eyes twitched as Harry toddled past him, chasing Nymphadora. Remus chewed his lip bloody when Minerva, in a rare moment of enthusiastic abandon, briefly swooped the toddler into her arms for a cuddle.
The two stared at one another, stared at their young ward, and stared at the ceiling so hard it nearly caught fire. They very, very barely— using every ounce of Marauder charm and deception they'd ever cultivated— made it through the evening. But eventually the Floo blazed green with the departure of their final guests, and the young men were left alone to address the proverbial elephant in the room.
"Remus?"
"Yes, Sirius?"
"Are you seeing what I'm seeing?"
"Afraid so, Pads."
The pair stared blankly at Harry, cuddled up on the couch with Pillowtop.
Sirius sighed. "You think Mopsy sees it?"
The soft pop of apparition signaled Mopsy's arrival seconds before the outspoken little elf was poking at the toddler's forehead. "Oh, Mopsy is most definitely seeing it."
"Do you think Aunt Cassie saw it?"
"Missy Cassiopeia is wanting to see you tomorrow. Mopsy is thinking she was definitely seeing it, too."
Remus and Sirius glanced at each other in dismay as a newly restored grandfather clock chimed 11pm from down the hall.
Harry blinked sleepily at them both from the couch, oblivious to both their ongoing dismay and the cloud of sticky dark magic around his own head.
March 3, 1982
Chateau Black, France
Cassiopeia Black stared at the messy child on her lap.
The messy child stared back.
"Pip, take note. Research subject 1534579– hereby referenced throughout as 'HPB'- displays an unusual curse scar that could be matched to several partial or complete runes. Per the ward schema of 12 Grimmauld Place, there is a particularly odd magic being contained within HPB directly behind the curse scar. It has been described by HPB's legal guardian as 'sticky and icky'- Pip, write this down separately: Sirius should not be allowed to pen his own speeches or contribute to my research notes ever again.
"Continuing: Special parameters around this research project include: interference to date by one Albus Dumbledore between the time the curse scar was obtained and the date HPB was retrieved by his legal guardian, the apparent hibernation of any Potter family magic remaining within HPB, and an absolute need to keep Marius from realizing HPB is a research project."
Cassiopeia released a long, loud sigh that was absolutely unbefitting either a researcher of her standing or the Black family Matriarch (her mother, had she had a soul, would be rolling in her grave). "Honestly, Marius is such a killjoy. I don't see why he can't understand that I have the most fun experimenting on family."
Behind her, Sirius choked.