Plot

Marshall and Lily think they've spotted Barney's doppelganger, which means that they can start trying to have a baby, but it's really Barney in disguise. Meanwhile, Ted goes blonde and Robin considers taking an anchor job in Chicago.

A couple of weeks after they make the vow to start a family if they see Barney's doppelgänger - the last of the five whose doppelgänger has not been seen - Lily and Marshall see that person in the form of a cabbie. They even telephone Barney to see if it isn't him in yet another scam to meet and sleep with women. They however decide not to tell anyone of their decision. When Marshall learns that the cabbie they saw really was Barney and not his doppelgänger, Marshall has by that time gotten into his mind that he really does want to start a family. As such, will he tell Lily the truth, she who seems to need that sign from the universe to embark on this important step in their lives? Meanwhile, Robin receives what she considers an offer for her dream job, that as a news anchor. The problem is that the job is in Chicago. Leaving her four friends would be difficult enough, but she isn't sure if she wants to leave Don, who she is finally meshing with both professionally and personally. She turns to an unexpected source for advice. And Robin, Marshall and Lily, using psychology, talk Ted into dying his hair blond by telling him not to do it.—Huggo

Although Marshall is ready to have a baby, Lily is not, so they reach a compromise: they make a pact to start trying to have a baby once they finally see Barney's doppelganger. One day, they finally spot Barney's doppelganger, who appears in the form of a brunette cab driver. Marshall even calls Barney at work to ensure that the person they are seeing is not Barney himself running some scam to pick up chicks. Marshall speaks to Barney on the phone, who says he is at work and hangs up

When talking about how Barney looks better as a blonde (in the absence of Barney), the gang convinces Ted to dye his hair blonde. Marshall later spots Barney's doppelganger again, and is about to thank him, but finds out it is only Barney's tactic to pick up women from the UN headquarters and sleep with them, to complete his list of sleeping with at least one woman from every country on the planet. But he forgot to account for the fact that chicks do not want to bang cab drivers. He says he has even recorded a generic enough message on his incoming phone at the office, that makes it look like he is always at work. However, Marshall doesn't tell Lily this as she is finally ready, but she finds out from Barney when she and Marshall are about to conceive a baby.

Meanwhile Robin and Don are becoming a popular network show host team. They are now co-hosting other programs for the channel as well, like Monty and Moo-Moo. Robin finally gets an offer for her dream job as lead anchor at rival station WNKW. The job is in Chicago, but she really likes Don. Ted counsels her that Robin has always been a career driven woman. When Barney finds out he takes Robin and Ted to Marshall & Lily, while they were about to have sex.. They are stunned as well, but Robin says she has decided to take the job. But when she talks to WNKW, she finds a photo of her and Don on the table and thinks that she needs to give romance a chance over her career. She refuses the offer.

Having nearly had to deal with Robin's departure, Barney realizes that the addition of a baby to the gang would not be that bad after all, and dresses up as an Estonian street performer (by the name of Kristof Doppelganger) in order to convince Lily that the fifth doppelganger has appeared. Lily and Marshall see through his act, but thank him for the gesture, assuring him that he will always be family. Barney finds another Estonian street performer, who swallows his entire sword. Barney nails her to close out the Baltics on his world map.

Robin is disappointed when Don tells her that he accepted the WNKW job. Heart-broken that Don was not willing to do the same for her, she breaks up with him and moves back to Ted's apartment. Ted tells her that although they have all been searching for their doppelgangers, things have changed so much in the five years since they first met that the five of them are now, in fact, doppelgangers of their own selves. Ted comforts Robin by saying she has become more courageous and that "doppelganger Robin" is amazing. They nearly kiss, but Robin bursts out in laughter when she takes off his cap and sees his blond hair again.

Four months later, Lily sees a street vendor selling pretzels who bears an uncanny resemblance to Barney and gathers the rest of the gang to witness the doppelganger, but they find that the vendor looks nothing like Barney. Just as Barney is about to protest, Marshall telepathically stops him. Future Ted points out that people can look for signs all they want, but usually only see what they want to see, when they're ready to see it, before Lily turns to Marshall and says "Marshall Eriksen, put a baby in my belly."