Sunday Six: The Mugging

Today's Sunday Six from Chapter Five of Rock Killer :

Charlie took the bag from her shoulder and held it out for him.  He reached for it.  Once he had his hand around the strap, she pulled back hard.  The boy was pulled off balance and Charlie grabbed the wrist of his knife-wielding hand and twisted hard. 
She was rewarded with a dull, moist pop as she broke the joint. 
He howled in pain and dropped the knife.