A public flameout forces 20-something alcoholic Sam to move back home with her overbearing mother, Carol; surrounded by all the triggers that made her drink, Sam tries to move past her worst self and figure out her best self.

An awkward run-in with her former best friend and her ex inspires Sam to own up for her past mistakes, both emotionally and financially; as she resets her relationship with her mother, Sam is horrified to learn Carol is dating.

Sam tries to win over Brit by making an amends at her birthday party. Unfortunately, Sam wasn't invited, and neglects Felicia. Meanwhile, when Sam's probation officer stops by, Carol struggles to explain Sam's "situation" to her friends.

Sam faces her hardest challenge yet: avoiding alcohol on St. Patrick's Day in Boston; Brit gives Sam an unexpected chance to rekindle their friendship; James and Mindy track down his lost keys while battling St. Patrick's Day temptations.

Sam embarks upon her first terrifyingly personal hook-up as a sober person with the help of Felicia, who has big plans to jump-start Sam's dating life; Carol "accidentally" plants a small seed of doubt in Brit's mind about Joel.

Sam scores a victory when she lands a job interview in New York with an unlikely ally, only to discover how scary it is to write while sober; concerned her daughter needs help, Carol breaks a boundary and introduces herself to Olivia.

Sam and James travel to New York. While there, Sam is confronted with memories of who she was before sobriety and must decide whether she can risk being Old Sam again. Olivia and Stephanie take an important step in their IVF journey.

In this flashback episode, an inebriated James meets a drunken "Katrina" in a bar on Thanksgiving. After getting kicked out, the two embark upon their own one-night holiday celebration. James' time with Sam spurs him to make a change.

After celebrating a milestone with a bang, Sam decides it's time to make amends with Carol. When a fight with Joel makes Brit re-examine the future, she turns to an unlikely ally: Felicia. Meanwhile, James conceals a destructive secret.

On her wedding day, Brit's jitters lead her to make an unexpected decision. Carol and Bob take their relationship to a new level. Sam learns the truth about James and is shaken to the core about what her future might hold.