In the story Lamb of the Slaughter the exposition is when Patrick walks into the house and is unushauly quite. This is the exposition because it makes Mary confused and sad.
The Rising action is when Patrick tells Mary some bad news. It is because this is where Mary gets angry. She goes into the kitchen and she grabs the closest thing she can find and while still looking happy she walks up to him.
The climax of the story is when Mary goes to the kitchen and grabs a leg of lamb and kills Patrick with it. This is the climax because now Mary has a problem and she has to cover it up.
The falling action is when Mary calls the police and acts as if she doesn't know what happened to her husband and she made an alibi that seemed to check out. This is the falling action because Mary pretends she has no clue what is happening advancing the story.
The resolution of the story is when the police eat the lamb that was actually the murder weapon. Mary says it would help her a lot if they ate the lamb. They hesitate but they do it anyway.
This scene is dramatic irony because as a reader we know that Mary is here for an alibi but Sammy the cashier thinks she is here to actually care for her husband. We know that she didn't help her husband. She only killed him.