When she went limp in his arms, Steve's face slackened too.

His face slackened, and his eyes were dull with an inward gaze.

It's at times like this that I can see how thin she is, when she's relaxed and her face slackens.

Glasser's face slackened as she caught up with Spock's line of reasoning.

His face slackened, its flesh a sack which was almost emptied.

The old man felt his deeply lined face slacken as a wave of sadness swept over him.

Then, gradually, her face slackened, as consciousness ebbed.

His face slackened as the realization of what might have happened punched through his anger.

His face slackened and paled, and he lowered his chin.

Her face had slackened and she was crying but without any sound.