"How I Met Your Mother" Season 9, Episode 9, "Platonish," reveals how Cristin Milioti's titular mother role helped Barney Stinson (Neil Patrick Harris) realise it's time to propose to Robin Scherbatsky (Cobie Smulders). This episode tells the story of how Ted Mosby (Josh Radnor) lost Robin.

Spoiler alert: This review recaps the highlights of How I Met Your Mother, Season 9, Episode 9: Platonish. Read at your own risk.

During the HIMYM Season 8 timeline (untold story), Robin and Lily (Alyson Hannigan) give Barney a series of challenges, all of which are related to picking up girls. Barney nails all the challenges, one of which is to ask for a girl's number while wearing a garbage bag, and without using the letter E in his spiels. Seeing that Barney doesn't want to stop "playing," Lily and Robin manipulate Barney to run an errand in pick-up challenge in disguise. Lily needs diapers; Robin wants samosas (Indian appetizer).

Barney Stinson to the 'mother' (Cristin Milioti): 'I don't know if I can just walk away from the game'

Barney Stinson meets the mother ahead of Lily, who has scenes with Cristin Milioti on her way to Farhampton for the wedding weekend. This is revealed in How I Met Your Mother Season 9, Episode 9, Platonish.

Barney gets some samosas and buys some diapers. He sees the mother as a target for his pick-up line. He walks up to her, but she gives him a surprising response. She makes him realize how sad he is. Chasing after women is his way of coping, the mother says. Barney tells her, "I don't know if I can just walk away from the game."

HIMYM Burning Question Answered: How did Barney Stinson meet the mother?

"Do you want to keep playing, or do you wanna win?" The mother asks the stunned Barney. Moments later, he's back at home, leaving behind the diapers and samosas. On that night, he revisits his playbook, and he begins a new page: The Robin. Viewers know the deal with Patrice (Ellen D. Williams) started after that, and then the proposal - engagement unfold later on. Ted Mosby's future wife has done something no other ex-girlfriend of Ted - certainly not Victoria - has done: Eliminate the competition.

Why no "Have You Met Ted" game?

Barney wonders if "the mother," apparently an insightful Lily 2.0, could meet any of his single guy friends. Ted Mosby doesn't come to mind. And he's never seen her again, she tells Robin, Lily and Ted in present-day Farhampton scene.

On the same HIMYM night, Ted and Marshall (Jason Segel) are watching a sports game. Marshall is pushing Ted to go after Robin so he can win his $5 bet against Lily. But Ted declares, despite his relationship being "platonish" with Robin, he's not going to ask her to pick things up again. "She's not going anywhere," Ted says. And that's how the mother put an end to Ted's analysis-paralysis chapter. In the end, Ted has no choice but to let go.

That same HIMYM night explains why Ted Mosby is itching to move to Chicago. As Barney recounts the story of the mystery woman, as well as the diapers and samosas, Ted realizes when and how he lost Robin. What he's about to realize is why that's a good thing.

VIDEO: How I Met Your Mother Season 9, Episode 10 - 'Mom and Dad' (Loretta Stinson and the Ex)

"How I Met Your Mother" Season 9, Episode 9, "Platonish," aired on CBS on Monday, Nov. 11. In Australia, the U.S. show is on fast track on Seven. Cristin Milioti's mother character still has no name, convincing viewers that this will be revealed in the HIMYM Season 9 and series finale.

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