User:SOTO/Forum Archive/The Reference Desk/@comment-188432-20130505035914/@comment-188432-20130506174530

From Tardis Wiki, the free Doctor Who reference

SmallerOnTheOutside wrote: Could you perhaps list the instances in which you think the script's referring to the leech or the venom as the Crimson Horror?

VASTRA: … and our greatest plague, the most virulent enemy, was the repulsive red leech
DOCTOR: Oooooh. "The repulsive red leech"! Nah, on balance, I think I prefer "the Crimson Horror". What was it, exactly?
VASTRA: A tiny parasite. It infected our drinking water. And once in our systems, it secreted a fatal poison.
DOCTOR: So it's been hanging around, lurking in the shadows. Maybe it's evolved. Maybe it's had help.

To me, this pretty clearly shows that they're talking about the creature being the Crimson Horror. I draw from this scene that the red leech is the Crimson Horror, but in other cases it's more the manner of death — as Doug points out – "ginned up" by the penny-dreadfuls.