After a night's rest (or rather, tossing and turning while Sirius snored peacefully), the two went back to the dungeons to collect their professor's remains.
"We really have to touch him?" Sirius squirmed at the sight of charred Slughorn.
"In order to be sure that he can never return, we have to scatter the ashes. I was thinking that we do it at the lake. It's dark, deep, and no one will ever want to go out there looking for him." Sirius nodded, disgusted as Severus swept up the ashes into a wooden bucket. Professor in hand, the boys walked up the spiraling staircase, through the enormous doors, and out to the lake. A boat waited for them, and securing the bucket in the middle, they pushed it out so that they could get in. Sirius did most of the rowing; Severus was still in shock that he had murdered his professor and that he had the need to do so in the first place.
When they had reached the deepest part of the lake normally reserved for the Giant Squid, Sirius stopped, rested the oars against the sides of the small boat and picked up the bucket. Severus looked into his eyes for second; the vampiric gleam had returned from missing his potion. Without a second thought, Sirius dumped half of the bucket to one side, and half to the other into the deep black water.
"You said the ashes had to be scattered. I wanted to be extra safe." Severus finally smiled at this, leaning in to kiss Sirius gently, as not to accidentally cut him and begin his hunger all over again.
"You are the perfect boyfriend, you know that?" Sirius blushed.
"Not as perfect as you are. You saved my life. But, how did you-?"
"I can't explain it, really. I just had a feeling that you were in danger. I felt it right here." Severus put Sirius' hand to his chest, directly where his beating heart should have been. Sirius smirked. Out on the lake, in the silence and soft yellow-blue of the rising sun, everything seemed as though it would be alright.
"Sev, what are we going to tell Dumbledore? I think setting your professor on fire may be against school rules."
"I thought you didn't care about breaking school rules? Sirius Black, afraid that he'll get house points deducted for being a naughty boy." Sirius stuck his hand into the water, splashing it on a laughing Severus.
"It's going to be okay, Sev. It's all over now." Severus smiled, kissing the back of the boy's hand.
"No. It's only the beginning."