The rising action in a story is known as the events in the plot that lead up or build up to the climax, or the highest point of action in the story. The rising action in the story actually comes very early because the climactic point in the story comes very early, the resolution takes up a larger than normal part of the story.

The rising action takes place when Patrick tells, a very pregnant Mary, that he's leaving her and she goes into shock. She acts like an automaton, it's as if she hasn't heard what he's said, or at least the statement he's made has yet to make its full impact. This event is what rises to the climactic point in the story in which Mary emerges from the basement with a frozen rack of lamb with which she uses to bludgeon Patrick to death with in one fell swoop.