There are a ton of hiding places in this ruin. Yu find a nice pile of rubble for her to hide behind a few rooms away. He tell her to keep quiet and that he will get back to her.
"Stay still and quiet here. We will return.. Well, if we do not return by morning, escape as best you can," Yu instruct her.
"Clever" Reg says as you leave her. "If the evil priests find Clara missing, they will not expect her to remain in the castle. With luck, they wil leave the castle altogether to find her."
"And we can explore unhindered" Yu say with asmile.