The Drunk Train
Lily and Marshall invite Robin and Kevin on a Valentine's Day trip to Vermont. Kevin and Robin use the trip to talk about taking their relationship to the next level. Meanwhile, Barney realizes he has finally met his match.
Bad Crazy
Ted is reluctant to break up with his crazy girlfriend Jeanette. Meanwhile, Robin becomes attached to Marvin after finally holding him for the first time.
Sweet Sixteen
Leslie realizes that the department has forgotten Jerry's birthday and decides to throw a party for him at a special location. Meanwhile, Tom is flabbergasted when he finds out Ann doesn't share his taste in music.
Li'l Sebastian
Leslie and the parks team put together a memorial service for a dearly departed friend. Meanwhile, Tom makes a big life decision, while Chris reacts badly to a health problem.
Galentine's Day
When Leslie hears her mom’s story about an old flame, she and her boyfriend Justin track him down and reunite them on Valentine’s Day. Meanwhile, Andy and his band are nervous about playing a gig at the Senior Center.
Bad Hair Day
Things get awkward when Phil shows up at Claire's college reunion. Jay is fixated on winning a big bowling tournament. A wig malfunction during an elaborate photo shoot with Joe leads to unfortunate results.
Virgin Territory
It's a day of disturbing realizations when Mitchell manages to ruin one of Jay's proudest golf moments, Phil overhears something that may forever change how he sees his little girl, and Gloria stumbles upon Claire's dangerous little secret.
Regrets Only
Phil and Claire have a huge fight and Phil hasn't a clue as to what it was over, so Gloria steps in to counsel Phil while Jay counsels Claire. Meanwhile, Jay has some regret in buying Gloria a karaoke machine, and Cameron is in full prep mode for a huge fund-raising event and asks Mitchell and Luke for help.
Fears
When Phil and Luke embark on a discovery expedition underneath the house, Phil tries not to let his fear of the dark and of creepy crawlies get the best of him. Meanwhile, Claire takes a nervous Haley to the DMV for her driver's test, Manny's sudden illness before a friend's amusement park birthday party makes Gloria suspicious, and Cameron and Mitchell invite Lily's pediatrician over for what turns out to be an anxiety-ridden brunch.
The Cohabitation Formulation
As Wolowitz contemplates taking things with Bernadette to the next level, Leonard rekindles his relationship with Raj's sister.