Lady Walks In A Pharmacy

A lady walks into the drugstore and asks the pharmacist for some arsenic. "Ma'am, what do you want with arsenic?" "To kill my husband." "I can't sell you arsenic to kill a person!" The lady lays down a photo of a man and a woman in a compromising position. The man is her husband and the woman is the pharmacist's wife. He takes the photo, and nods. "I didn't realize you had a prescription!"