Robin tells Barney she is late and that he is the likely father. A trip to the doctor reveals she is not pregnant but the doctor asks to see her again and delivers the news to Robin that she won't ever be able to have children. Instead of telling her friends the truth she invents a story to explain why she seems disappointed. Marshall meanwhile gets into the Christmas spirit and heads out to their house in East Meadow to decorate. After enlisting the help of a local boy, he is betrayed and stranded on the roof until Lily comes to visit.