How I Met Your Mother’ season 8 becomes obsessed with its fifteenth episode of the penultimate season “P.S. I Love You,” as Barney uncovers a new chapter of the Robin Sparkles saga in his quest to identify Robin's past obsession, while Marshall and Lily try to convince Ted his new girlfriend Jeanette ('SNL's Abby Elliot) is a stalker.

Last time’s ‘How I Met Your Mother’ episode “Ring Up!” saw Ted dating a much younger woman (‘Pretty Little Liars’ Ashley Benson) at Barney’s insistence, while Robin lamented that her engagement ring made her invisible to men, and Marshall found a hazardous way to spice things up with Lily, so what did tonight’s all-new episode bring?  Are we any closer to learning how the final years for Ted, Robin, Barney, Marshall and Lily play out?

Read on for your in-depth recap of everything you need to know about ‘How I Met Your Mother’ season 8 episode 15, “P.S. I Love You!”

Ted recalls how one day he was just about ready to give up on finding the one, he spotted a girl across a subway car reading the same book as he, but failed to find anything to say to her before she left the train. He shows Marshall and Lily how he wrote down whatever details he could to find her, but they dismiss his actions as stalking and an attempt to force destiny. But later that day following a school fire alarm, who should he find outside, but the girl from earlier!

While Marshall and Lily continue to have their doubts, the girl Jeannette seems to have stalked Ted in much the same ways as he had, the fire alarm being serendipitous enough to send him outside the building she’d been turned away from. Ted professes her stalking to be cute and mutually appreciated, more Lloyd Dobler of ‘Say Anything’ than Jeffrey Dahmer, but the others point out Jeannette likely pulled the fire alarm herself.

Robin in particular agrees to cut Ted a bit of slack, considering she herself once stalked someone back in Canada to the point of a restraining order, but Barney’s condescending attitude prevents her from revealing the crush’s identity. The idea of Robin’s obsession quickly drives Barney over the edge, breaking into her bedroom and pouring over her diary to find the phrase “P.S. I Love You” scrawled everywhere. To Canada, for the truth!

Meanwhile, Ted gets Jeannette to admit she pulled the fire alarm because she couldn’t stand the idea of coming all the way to the school and not meeting Ted. However, upon inspection of the building, Marshall and Lily point out that the building doesn’t have regular fire alarms, meaning she would have had to have started an actual fire in a trash can to set off the smoke alarms.

At a Tim Horton’s in Canada, Barney follows the trail of Robin’s ex-boyfriends all the way through to Simon (James Van Der Beek), who reveals that Robin’s obsession went back to her 1996 meltdown at the Great Cup. Intrigued, Barney learns that all the information he needs can be found in a copy of “Underneath the Tunes” chronicling the downfall of Robin Sparkles!

Ted reveals that Jeannette admitted to going a step further and starting an actual fire, but Barney interrupts everyone to reveal his copy of the Robin Sparkles tape! All except Robin gleefully sit to watch the video, which sees a host of Canadian guest stars remembering Robin Sparkles’ earlier days, and ultimate re-birth into the grungy, Alanis Morissette-style singer "Robin Daggers." All the Canadian celebrities, from Dave Coulier to Paul Shaffer recall their horror at seeing Robin Sparkles become Robin Daggers at the Great Cup, ending her career. But who do the celebrities think was the object of her grungy song  “P.S. I Love You?” Most seem to agree on…TV’s Alan Thicke!

Sometime later, Barney returns to the apartment having soundly beaten up by Alan Thicke, though Alan revealed he wasn’t the subject of Robin’s obsession. Barney begrudgingly concedes to Robin that anyone can get an obsession, and Robin finally admits her stalker obsession as…P.S., Paul Shaffer! The pair make up, but when Marshall uses the reconciliation to point out to Ted that Jeanette is much crazier, Lily admits her own secret. Years ago at college, she didn’t randomly meet Marshall by asking him to fix her stereo, but rather saw Marshall at orientation, broke her own stereo, and knocked on a number of doors hoping to find him.

With Marshall’s blessing, Ted goes to see Jeannette once more, only to realize she’d followed him to the bookstore before they even met on the subway, and bought the same book on purpose. In fact, she’d been following him ever since his New York Magazine cover a year and a half prior! Future Ted admits to making one final horrible mistake before meeting the children’s mother, as present Ted passionately embraces Jeanette (and her stalking).

Over the credits, more of Robin Daggers’ grungy video is revealed. Hey look, the robot!

As the first 'How I Met Your Mother' episode to air since the official announcement of the show's ninth season, there isn't much to read into about "P.S. I Love You" and its overall impact on the series. Ted does have a line about Jeanette being the "last" horrible mistake he made before the mother, but it's likely a subjective statement. Instead, the episode is just good plain fun, placing a potentially final cap on what had been one of the series' best recurring gags, and bringing in some great guest stars to do it. Overall, "P.S. I Love You" needn't feel any more than an entertaining palate cleanser before the ultimate arc of the season begins to take shape.

Was ‘How I Met Your Mother’s latest “P.S. I Love You” a triumphant return, or a tragic downward spiral?  Do you think it made for a solid entry to the penultimate season? Join us next week for an all-new episode recap of ‘How I Met Your Mother’ episode “Bad Crazy” on CBS!