It is bad to go behind someone's back
Violet's mother doesn't allow sweets before dinner, but Violet's grandmother is visiting and doesn't know the rule.
Violet wants a cookie.
Violet asks her mother if she can have a cookie after dinner.
Violet asks her grandmother, who gives her a cookie just before dinner's ready.
Violet's mother gives her a cookie along with her dessert.
Violet's mother finds out, and Violet gets no dessert for the next two days in punishment for breaking the rules.