In an attempt to deliver a devastating final slap to Barney, Marshall explains how he mastered the Slap of A Million Exploding Suns.
The gang encounters a guy at the wedding who intentionally stirs up trouble among them, and Marshall finally arrives at the Farhampton Inn.
Barney is shooting to have the rehearsal dinner at a laser-tag venue, while Lily is upset when Ted fails to live up to a promise.
Marshall tries to get Marvin to sleep by reciting three rhyming bedtime tales about his friends as they wind down their epic cross-country journey.
When Barney’s father arrives at the hotel, Barney devises a plan that makes Robin very nervous. Meanwhile, Ted is convinced someone framed him by messing up a wedding-related duty.
In a flashback episode, the gang ponders the future of the Ted, Robin and Barney love triangle. Meanwhile, Barney accepts a series of challenges from Lily and Robin.
When Robin and Loretta’s conflict escalates, Barney is caught in the middle. Meanwhile, Marshall and Daphne deal with a stowaway on their road trip, and Ted and Cassie try to enjoy a trip to a lighthouse.
When Daphne sends a troubling text message to Lily, Marshall enlists the gang’s help to remove the message while enforcing the “No Questions Asked” rule.
When Ted finds himself with three prospects to be his date for the wedding weekend, he chooses poorly. Meanwhile, Barney and Robin have a confrontation with their minister, and Marshall learns more about his driving companion, Daphne.
When Barney is forced to pick sides in a fight between Robin and his mother, Lily coaches him on how not to ruin his relationship. Meanwhile, Ted and Marshall get into a dispute over wedding gifts and thank-you notes.