it was a new case for them, they needed to solve a mysterious case.. That involved you.

the next night, you were out thirsty for blood. You weren't human. You must go feed someone off.

that was until Sebastian found you. Ciel decided to not kill you but instead he ordered Sebastian to lock and chain you up in a room.

Sebastian has visited you after a few hours.

"ehem. are you awake?" he says as he steps in.

(I'm still in season 1 so sorry if I made any errors)