She asks the pharmacist for cyanide.

Pharmacist: “I can’t sell you that. It’s a deadly poison.” Lady: “I know. I want to kill my husband. He’s having an affair.” Pharmacist: “I don’t care. I can’t sell you cyanide.”

Lady shows him a picture of her husband and the pharmacist’s wife in bed together.

Pharmacist: “Oh … you have a prescription.”