Marshall claims that he had the best hamburger in the world during his first week in New York City, but he forgot where the burger joint is located. The gang then hits the streets of Manhattan to help him find it.
Ted tries to keep his irresponsible sister from hooking up with Barney during her trip to New York, and Robin starts hanging out with Marshall at a bar for Minnesotans, not telling them that she's really Canadian.
Ted and Robin discover that sex with each other solve their fights as roommates, which makes Barney very jealous and angry. Meanwhile, Marshall reveals that he's too embarrassed to use the office bathroom.
Ted meets with his ex-girlfriend from college--a girlfriend who cheated on him constantly and Marshall and Lily can't stand, and Marshall tells the story about how he forgot to bring his pants to work.
Ted's plans to make his own design firm in his apartment hit a snag when his personal assistant begins sleeping with Robin, and Marshall tries to find a way to make himself indispensable at his workplace.
While Ted struggles with an unorthodox architecture project, Robin finds out that Barney is in love with her, and Marshall threatens to take a long-considered leap from the roof to a neighboring building.