The boy's mouth jerked suddenly into the brief, mirthless twist of a smile.
Beneath the mask, his mouth jerked open to yell.
His mouth jerked unpleasantly as he recognized his younger brother.
Martin's mouth jerked; he might have been trying to smile.
His drooping mouth jerked upward in what might have been an attempt at a smile, and he went from the room.
"She said-" Abruptly his mouth jerked into a crooked smile.
They looked like mannequins to him, their mouths jerking as if worked by wires.
Her mouth jerked downward at one corner.
His hard mouth jerked the cigarette in it once.
His mouth jerked as if she had slapped him.