Nothing more could be done. Either Artemis was safe, or he was not. If not, Butler was in no condition to fulfill the terms of his contract. This realization brought tremendous calm. No more responsibility. Just his own life to live, for a few seconds at any rate. And anyway, Artemis wasn’t just a Principal. He was his only true friend. Madam Ko might not have liked this attitude, but there wasn’t much she could do about it now. There wasn’t much anybody could do.
