[ Abruptly, Spock stands. He brushes off his fingers even though they did not actually touch the vat. Without looking at Kirk, he moves to a door on the other side of the room and begins examining it for signs of use. His tone, when he speaks, is the same as it has been despite the strangeness of his words. ]

I was unaware of the true level of danger here. In asking you to prove yourself to me, I do not intend to ask you to die to do so.

[ Perhaps "Roger" is not the harmless, moral vampire he claims to be. It does not matter. Spock cannot draw him into danger he is unlikely to walk away from. If the nest is so old as this room suggests, he will not be able to protect the other man. He will only be able to care for his own life. ]