The gang discovers that Robin's been hiding a huge secret, but they have no idea what it is. Marshall thinks she is married, and Barney thinks she was a porn star.
Will Ted go to the opening of his new building with Robin as his date, or will he break his promise to Barney and tell her that Barney is proposing to Patrice? Meanwhile, Marshall and Lily have big plans for a rare night out.
When Barney hooks up with a woman Lily had been saving for Ted, she gets revenge by stealing his "playbook," which contains all the moves he uses to pick up women. But will Barney have the last laugh?
When Ted leaves the bar early to prepare a Thanksgiving feast for his friends, the gang winds up partying all night with The Blitz, an old friend from college who has bad luck. As a result, Ted is forced to spend Thanksgiving with Zoey.
The guys shatter Ted's impressions of his new girlfriend by telling him she talks too much. Ted responds by turning the tables on his friends, and they react by pointing out Ted's worst flaw.