Randall — or should we say Kyle — was faced with a difficult decision in Season 1, episode 3 of NBC’s “This is Us.” He could either continue hiding his newfound relationship with his biological father William or be honest with his adoptive mother, Rebecca, and deal with her heartbreak.

He chooses the latter, pulling his mom aside to share with her that he has found his father and invited him to live with himself, wife Beth (Susan Kelechi Watson) and their two daughters. Rebecca (Mandy Moore) appears saddened by the news, but takes it in stride, asking to have a face-to-face with William (Ron Cephas Jones). Randall (Sterling K. Brown) takes her to the room in which William is hiding, which comes a surprise to his father. Rebecca then does something no one could have seen coming — she asks for a moment alone with William. Randall obliges, backing out of the room and retreating to find his wife.

Rebecca immediately begins laying into William, making him promise not to hurt Randall again. She tells him that he is her son and, as such, she knows he’s going to pour his heart and soul into forging this relationship and helping to make William better — he will put it before everything in his life, including his wife, children, and prestigious job. She tells him to take a look within himself and asses whether he’s worth Randall’s effort before putting any strain on his family, alluding to a deal that they had made years prior.

Yes, that’s right — this isn’t the first time William and Rebecca have met. Flashbacks during the episode, titled “Kyle,” reveal that Rebecca sought out Randall not long after she and Jack (Milo Ventimiglia) brought home Kevin, Kate and Randall — then known as Kyle. She tracks him down through a bus driver and meets with William at his home, where she is able to pull some information about his relationship with Randall’s biological mother. William gifts her with a book of poetry by a writer whose last name is Randall, which he used to read to the mother of his child. Rebecca takes it home with her, later presenting it to her husband while suggesting that they change Kyle’s name to Randall. Rebecca seems to believe that doing so will not only help her and the baby connect, but make him “hate” her less.

Meanwhile, back in the present, William is left questioning his new relationship with his son. Rebecca and Miguel (Jon Huertas) leave and Randall heads upstairs to check on his dad only to find that he’s suddenly gone missing. He hops in the car and begins combing the neighborhood for his missing father, whom he finds walking not far from the house. Randall orders him to get in the car, reminding him of the trouble he’s gone through to get him appointments with good doctors to treat his cancer. William agrees, but the doctors have nothing but bad news for he and his son. Once home, Randall apologizes for the way things went, telling him that he has decided it’s time to come clean with his kids about William’s identity.

“This is Us” creator Dan Fogelman opened up about William, Randall and Rebecca’s confusing connection during a recent interview with Entertainment Weekly. He called the plot twist the “biggest story” of the season, adding that it centers on the differences between what is really going on in Randall’s life and the way he perceives it. Fogelman said that viewers will be gifted with more details about Randall’s adolescence, and how his biological father’s absence effected it, during episode 4. While he was not able to give much away, he told EW that we will soon further explore “this false narrative that’s defined him.” Fogelman said that at a young age Randall started asking questions about his biological parents, as any adopted kid might. His questions will create a segue into how Rebecca came to find William in “This is Us” flashbacks.

As photos from Season 1, episode 3 of “This is Us” revealed, “Kyle” was about far more than just Randall being honest with his mother about William. Kevin (Justin Hartley) was struggling after quitting his acting job. With nothing holding him back, he decided to make the jump from the West Coast to the East Coast, looking into apartments in New York. He assumed that Kate (Chrissy Metz), who does everything for him, will move too, which doesn’t sit well with her new beau Toby (Chris Sullivan). He sets out to prove to Kate that she’s just as important as her brother, but his grand gesture is not well-received.

“This is Us” will return with a new episode Tuesday, Oct. 19, at 9 p.m. EDT on NBC.

rebecca_thisisus Rebecca (Mandy Moore, pictured) reveals a secret link to William (Ron Cephas Jones) in Season 1, episode 3 of the NBC drama “This is Us.” Photo: NBC