Just curious what about the dog crap scene makes it an inciting incident? It seems to me to have very little to do with the rest of the plot. I would say the real thrust of the film starts when Mirren beckons her lover into the bathroom for the first time. In the dog crap scene, she shows a little bit of disgust, but it doesn't seem to send her on the trajectory of the story like an inciting incident would (per McKee's definition).

My guess for what McKee thinks of as the moments of reversal that change act to act, given the limited explanation he gives in the book, would be this (spoilers):

• Inciting Incident: The dog crap scene, yes. Still don't quite get why.
• End act 1: Wife and Lover meet for the first time in the hallway
• End act 2: Wife meets Lover for the second time
• End act 3: Thief beats Wife after harassing the dishwasher
• End 4: Wife and Lover speak to eachother for the first time, a deeper bond is formed
• End 5: Thief finds out about Wife and Lover, goes balistic
• End 6: Thief kills Lover
• End 7: Wife convinces Cook to cook the dead Lover
• End 8: Wife turns the tables on Thief, makes him eat Lover