 On Halloween, Robin and her new boyfriend Mike meet for a Double Date with Lily and Marshall, who are eager to win the costume contest. Robin turns out as someone who is not so much into "couple things" so the dinner is not as pleasant as expected. Barney actually wants to take Ted with him to a Victoria Secret s Party, but Ted heads for a party on the roof of his apartment house, where he a few years ago met a beautiful woman, which is just called the "slutty pumpkin". Eager to meet her again, because he never had the change to call her because he lost her number, he waits for her every year at this party.