He stood listening for a moment, then his expression altered.

The expression on the face of the little Chinese did not alter.

His expression altered as a knock sounded on the door.

He leaned back, and his expression altered from worry to surprise.

She paid no attention, and his expression altered to a more contemplative one.

She showed him her hands and his expression altered to one of real concern.

It was a good beginning, but when he returned his expression had altered.

Then his expression altered as he looked down at her.

Then he was pushing her toward the medical unit, his expression altered to one of deep concern.

Her expression didn't alter, despite the bite in his question.