English Idioms: He should crack the whip

Dialogue
Mike: Why

are you down in the dumps?

Suzan: Carl has foiled all our plans. I was going to take a few days off work but he turned down my request on the pretext of a due deadline and that they cannot do without me for the time being. 

Mike: You’re kidding! If your husband heard that, he would hit the ceiling.

Suzan: He must step in and put a stop to Carl’s arrogance. He’s the company’s owner after all and he should crack the whip.

Vocabulary

Down in the dumps: discouraged, depressed, or sad.

Foil a plan: to spoil a plan; to cause it to fail.

Turn down:  to refuse someone's request.

On the pretext of: a false reason used to explain why you are doing something.

You’re kidding: You cannot be serious; I don't believe it; this can't be true.

Hit the ceiling: to explode in anger; to go crazy. Step in: to become involved in a difficult situation, especially in order to help.

Put a stop to: to cause to end.

Crack the whip: to use your authority to make someone else behave better or work harder.