He's looking for Colonel Sapt.
The King has been walking in the drive, and learnt from a sentry of Rischenheim's arrival.

I told the man that you had taken the count for a stroll round the castle, and I did not know where you were.

He says that the king may come himself at any moment." Sapt considered for one short instant; then he was back by the prisoner's side.
"We must talk again later on," he said, in low quick tones.

"Now you're going to breakfast with the king.

I shall be there, and Bernenstein.
Remember, not a word of your errand, not a word of this gentleman! At a word, a sign, a hint, a gesture, a motion, as God lives, I'll put a bullet through your head, and a thousand kings sha'n't stop me.