The episode begins and Claire's disappointed, the Dunphys did not decorate their house for Halloween. Actually, a neighborhood petition banned it. She couldn't even carve a pumpkin; the petition was very specific as it turns out. Given she scared a lot of kids last year and gave one parent a heart attack with her Alien-inspired costume; they are out of luck this year. She really wanted to scare the trick-or-treaters; she even used professional-grade makeup. Cameron and Mitchell are trying to get their Halloween costumes right because Cam has lost some weight. The costume shop still figured Cam would be the bull and Mitch the matador, but there's actually a bigger problem.
Lily wants to go as a princess again because a tired Mitchell once told Lily her real mom was a princess and was very busy, so she let Mitchell and Cameron take care of her. Mitchell didn't know she would hang onto a bedtime story like that, but she did. Since Mitch doesn’t own up to it, Cam can’t figure out why Lily is so obsessed with being a princess. Jay is unable to charm his way out of a ticket. Manny on the other hand has picked up some street cred with the other students. Turns out, to clear his mind for a test, he was practicing his Gene Kelly dance moves in the hall and he accidentally hit the fire alarm. Because of that, all of the students didn’t have to take a test and are grateful to him because of it.
One of his friends tells him, not to join them at the park later because he has to apologize to the whole school, on Monday. Luke though, says it is a chance to get in with the cool kids. All the kids are avoiding the Dunphy house for trick-or-treat. Clair even tries to go out in her Little Bo Peep costume to pass out "brand name candy" but only ends up snagging a little girl by accident with her staff and makes her parents think it is a kidnapping. At Mitch and Cam's, they are throwing a party, Cam is beside himself because nobody can see he has lost weight under the bull costume. He therefore resorts to 'flashing' everybody so they can see his body. Lily suddenly spots her mommy.
Actually, she has spotted someone in a princess costume and Mitch has to explain that the woman in the princess costume isn’t her mommy. Phil isn't having much more fun trying to run an open house on Halloween. His logic is to pass out candy to the kids and get the bored-out-of-their-mind parents to look at a nice place. That really doesn’t work, and Claire is just as lonely after being shunned by the neighborhood. Suddenly, Claire has an idea. It’s an Empty house, and Phil is by himself. Claire decides she needs to convince Phil, she can be scary. Well, it turns out it's a lot harder than it looks. Somehow, Claire doesn’t manage to scare Phil, but she does leave her Little Bo Beep staff at the door, so now Phil thinks Claire snuck into the house.
Jay and Gloria join Mitch and Cam, who has changed into a Mr. Roarke costume from Fantasy Island so people can see he has lost weight, only to be upstaged by someone who had lost over 100 pounds. Jay has to restrain Gloria, who is told she must be dressed as an illegal alien, since she is wearing an alien costume. Jay tries to tell her to calm down anyway, mainly because the baby is affecting her mood, and she thinks the baby is angry inside of her. She begins freaking out about it. But Jay says being defensive about her baby makes him think she'll again be a great mom, which makes her feel better. But then the two punks who left dog crap on their lawn earlier arrive and Jay decides a couple of rotten eggs won't hurt the baby much. Phil starts looking around the house for Claire.
But then actual customers come by, and now Phil is afraid Claire will pop out and scare them. Phil then goes crazy trying to keep the couple away from Claire. At the party, Lily tells the princess her mommy was one, too, and now Cam wants to know what's going on. Mitchell finally admits the truth, and Cam brushes it off quickly, mostly because he's told a few tall tales himself. They decide to tell Lily the truth that they don't know where her real mommy is. But they convince her, her mommy wanted to put her with the most loving family she could, and she did. As a reward, Gloria lets the princess hit on Jay for a few minutes to make him feel better about still being charming. Jay later compliments Cam, on losing weight.
After the couple has seen the house and left, scary things begin to happen in the house. In the end, after Phil is scared out of his wits, he discovers that it’s Claire and Alex who are doing all of it. The episode ends at this point.