Barty had taken the knife back by the time Nathan came back to life. "You haven't done this a lot, have you? That was a pathetic show." Clearly not someone who knew where to stab for a quick death. "I gave you a proper instrument and it still took you so long. It's like that time I had someone gouge their own eyes out with a spoon, that was unexpectedly lengthy as well."

Checked out with Nathan's story about his powers being new. Why would that be happening? "Let's see how fast you learn."

He held the knife out. "Stab yourself to death again, darling."