Ted's family's visit to New York leads to the discovery of a family secret; Lily and Marshall struggle to get used to their new relationship.
After Ted and Robin have their first big fight Barney convinces Ted that being an architect is a great way of picking up ladies.
The gang tries to take Marshall's mind off his break up with Lily. This isn't helped by Marshall finding a credit card bill with some of her charges listed.
Ted sees through Lily's stories about the fun and excitement she found in San Francisco, and Robin is surprised to learn the real reason Lily came back.
Two weeks before their wedding, Lily and Marshall attempt to live apart to sort out last-minute preparations. While at Robin's house, Lily discovers that she's lost weight and no longer fits into her dress.