Question, and I'm having a hard time recalling instances where it happened though it may have, but is it just me, or did the Doctor just kill a human being? Not through the person refusing help, but actively, locking a human being in a space ship with a target marker that will draw in missiles to kill the human? That was .. cold. He certainly killed aliens who were getting cheeky, like the Sycorax who was going to stab him in the back on the edge of the ship, but I'm having difficulty remembering him killing a human like this before.