The king is worried because he is ill.
He suddenly aged, eaten away by an unknown and unnatural evil.
Here is a fragment of what he says in a low voice, when he is alone: "I am convinced... that some malevolent being is attempting to wrest control of my thoughts away from me. Voices direct me to horrendous acts, and there are times when I seem unable to control my body. Lazarus knows; this is certain. He looks at me strangely when he thinks me otherwise disposed..."