Takes place sometime before the S1 finale if we're talking anime terms, but if manga it's just anywhere before the Zombie/Ship Wreck arc.
Ciel drops the teacup. He's just curious, really, he tells himself as he watches the elegant porcelain cup shatter. He has an estimated guess of what will happen, but all the same, perhaps he is wrong.
He is not.
Sebastian enters the room immediately, and Ciel feels tired again. It never changes, not really. He has always known this. Sometimes, though, he can't help but dream, just a bit. During sleepless nights, he reckons what it would be like if perhaps, things were not always the same. If possibly, Sebastian ever dropped his butler facade and let his demon side show again.
Ciel knows he won't. That is his life, and it is in Sebastian's efficient nature to never appear more than a concerned - if not slightly taunting - butler. It cannot be helped. Today, he comforts himself with the knowledge that when his revenge is finally accomplished, he will see Sebastian in all his demonic glory. He will be disgusting and hideously beautiful and Ciel will not be able to think literately anymore and he won't say goodbye. Sebastian will have his soul and it will but gorgeously painful, because Ciel was never really sane, was he?
As Sebastian picks up the teacup's fragments and cleans the spilled earl grey, Ciel's mind speaks for him, murmuring, "Goodnight, then. In the most twisted sense, I suppose it was a day worth living."
Sebastian's eyes widen for a moment. Ciel smiles wryly.
He has finally gotten the reaction he desires.