A lady goes into the local pharmacy.

Lady: I want to buy some Arsenic.

Druggist: I’m sorry, I can’t sell you Arsenic. Why do you want it?

Lady: I want to kill my husband.

Druggist: Heavens, why would you want to kill your husband?

Lady reaches into her purse and produces a picture of the druggists wife and her husband in bed together.

Druggist: Oh, I didn’t know you had a prescription.