Work Text:
Sometimes when sleep eludes him, Albus corners it through an evening constitutional through the passageways. Invisible, he passes by boarded-up wings given up to the ghosts and into the heart of the castle, where muted voices lull him through the bricks.
He often stops in the dungeons, at a certain spot where the cracks in the mortar part slightly for him. Perhaps he's just in time to watch Severus undress for bed, a slow unbuttoning of public appearances. Perhaps Severus is sleepless as well and pauses between robes and nightshirt.
Pale hands and a well-formed cock...
They both retire satisfied.