When a perfect girl finally shows up, the gang tries everything to help Ted, while Marshall takes action when he discovers a letter written by younger himself.

When Lily refuses to believe that Jenkins, Marshall's attractive female colleague, kissed him, Marshall insists Jenkins tell Lily what really happened. Meanwhile, Robin finds out that a drinking game has been made up about her.

When Zoey enrolls in Ted's class, she manipulates his students into taking her side in the fight to save the building being torn down to make room for his project. Meanwhile, Marshall and Lily spot Robin marching in the Halloween parade of shame.

Barney meets his father and is shocked by the differences in their lives. The rest of the gang learn their "gaps"; knowledge they should have by now, but don't.