On their 36th birthday, a group of people faces events that change their lives forever: Jack's wife Rebecca goes into labor; Kevin makes a shocking professional decision; Randall confronts his birth father for the first time; Kate renews her resolve to lose weight.
As Jack and Rebecca contend with marital issues, Kevin braves his strained relationship with Randall to ask for his brother's advice. Beth is unsure that William has honest motivations for joining her family.
Jack and Rebecca struggle to bond with their adopted son. William's past and the reason he abandoned Randall are revealed. Toby challenges Kevin and Kate's codependent behavior.
The Pearson's day at the pool takes a turn when their three children struggle to feel like they fit in. Toby and Kate's date is interrupted by a familiar face from Toby's past, but the encounter threatens to send them spiralling.
William helps Kevin overcome his self-doubt. Jack and Rebecca have a fight about having children. Kate reveals a painful part of her past to Toby.
Kate's new job proves challenging because of her boss's daughter. Kevin receives a piece of unexpected advice from Olivia. Randall feels alienated by his inability to explain what he does on Career Day.
Old tensions between Randall and Kevin surface when they are forced to have dinner alone. A bonding moment between Beth and William reveals a secret to Beth.
Kate's struggle with her weight puts a strain on her and Toby's relationship. Beth confronts Rebecca about withholding information about William from Randall.
In an attempt to deal with his mother's lies, Randall and his siblings take a trip together. A vision of Jack gives Randall a new prespective on Rebecca's actions.
The Pearsons band together to help a familiar face. Randall's Christmas party ends on an unexpected note for Kate and Toby.
Randall struggles to accept that William is taking precious time away from their family to spend with Jesse. Olivia's return puts a strain on Kevin and Sloane's relationship.
In the lead up to the triplets' birth, Jack, Rebecca, Dr. K, William, and the fireman who brought Randall to the police station struggle with their own personal issues.
The Pearsons' attempt to have separate birthdays for the Big Three backfires. Encouraged by advice from Toby, Kevin makes an attempt to reconcile with a face from his past.
Jack and Rebecca are shaken by Miguel and Shelly's divorce. Randall threatens to crumble under pressure. Toby's visit to Kate in the camp doesn't go as planned.
Jack and Rebecca clash when the former tries to stop her from pursuing her dream. Kevin faces a difficult choice between his brother and his play.
William's past is revealed as he takes Randall to his hometown. In a time of crisis, Randall finally reconciles his connection to both his biological and adopted fathers.
The Pearsons deal with the aftermath of William's death. Randall makes a shocking professional decision. Kate reveals a secret about Jack's death.
Jack tries to reconcile with Rebecca but the meeting goes awry. Randall's soul-searching leads to a surprising decision. Kate resolves to pursue her passion.