Okay, so Jeremy is Sebastian in disguise.
I guess I feel a little better about his role undermining Doyle's, then...
But seriously, Ciel helping him pull the old switcheroo when examining Sebastian's corpse, "I do not tell lies," helping the servantrio cook, "Earl, take off your clothes..." It's classic Sebastian! BE MORE OBVIOUS, DEAR. <3
Still wish he'd picked a better pseudonym, though!
...BUT WHO IS THE KILLER??