The man's expression stiffened and he glanced back at Vimes again.

Cecelia's expression stiffened even more.

Jeremy's expression stiffened, but the light was too poor for her to read his eyes.

The captain's expression stiffened a little and he asked, "Are you one of the Pritts crowd?"

Then, from the way his expression stiffened, it was clear he regretted his remark.

Her expression had stiffened.

The old man's expression stiffened.

On a relatively minor matter, Congress has put its integrity on trial; an expression of outrage from constituents might stiffen some backbones.

Alexander did not smile back, and her own expression stiffened ever so slightly.

Patricia's expression of joy stiffened.