What are the most five important scenes in "Lamb to the Slaughter"?

While this question is open to interpretation, 5 crucial moments that develop and resolve the conflict can be identified.  This is how I see them:

1) Patrick drains his drink, and refuses dinner.  Mary becomes aware that there is tension because of this.

2) Patrick announces his desire to leave his pregnant wife.

3) Mary kills her husband with the frozen leg of lamb.

4) Mary calls to police to announce that she has "found" her dead husband.

5) The police eat Mary's dinner, including the leg of lamb, and theorize about the murder weapon.

Dahl really ends on an ironic note here, with the investigators not aware that they are eating the murder weapon.  Readers are left with the understanding that Mary will be spared.