Barney: I know Robin's secret. Barney: Oh. Slap bet. Ted, Marshall: To the Willowbrook Mall! Ted: You know how to make crepes?
Plan: A: Barney; Q: Who uncovers Robin's secret past? A: malls; Q: What does Robin have a strong aversion to? A: Marshall; Q: Who does Barney make a bet with? Summary: Barney uncovers Robin's secret past and the real reason behind her strong aversion to malls, which leads Barney and Marshall to make a bet.