In their parallel conversations with Diana and Natalie, Dan and Henry reaffirm their promises to stand by their partner, no matter the circumstances (“A Promise”). Dan acknowledges that while he is no longer the boy who made his wedding vows to Diana, he hasn’t forgotten those vows as a man.

The vision of Gabe appears once again to Diana, beckoning to her (“I’m Alive (Reprise)”). As Diana acknowledges Gabe’s presence, Dan tries to convince her that Gabe isn’t there. Diana tries to escape, meeting with Natalie on the staircase. When Natalie tells Henry that she needs to take Diana to the doctor, Henry offers to help. Natalie declines and assures Henry that she will look for him at the dance if there is time to catch up.

Diana meets with Doctor Madden, commenting that while her treatment has cleared her mind, it hasn’t fully resolved her issues (“The Break”). Doctor Madden reassures her that the relapse of delusional episodes is a common occurrence. Diana reflects that none of the medical options can really heal her wound, which is not in her body, but in her soul. Doctor Madden suggests continuing Diana’s electroconvulsive therapy to strengthen its effects (“Make Up Your Mind / Catch Me I’m Falling (Reprise)”). Diana is reluctant to continue pursuing treatment, especially when Doctor Madden’s assurances remain non-committal. When Doctor Madden suggests trying medication therapy once more, Diana asks to consider other alternative pathways. She expresses skepticism over the way her grief has been classified in psychological literature, especially considering the intense stimulus for her grief. Doctor Madden urges Diana to continue seeing him for talk therapy. Diana chooses to part ways with him.

Diana shares her decision with Natalie and informs her that she will be taking her to her dance. She assures Natalie that it is time for her to consider her own happiness for a change. Natalie worries about Diana’s decision. Diana shares her resignation with Natalie, explaining that she has become tired with the way her life has become focused on treatment for so many years (“Maybe (Next to Normal)”). She sympathizes with Natalie and hopes that she can one day break the cycle of grief she has inherited from her mother. Natalie is surprised by Diana’s sympathy, which she has yearned for all her life. She acknowledges Diana’s desire for Natalie to escape her grief.

Mother and daughter embrace as they tentatively hope for each other’s lives to improve. Diana promises to work towards letting go of her grief and being present for Natalie. Natalie doubts Diana can do this. Diana then reveals the truth about Gabe to her for the first time: At eight months old, he died because of an intestinal obstruction. Natalie expresses her need for a life that is “next to normal” (94) so that she can function and survive, acknowledging that “normal” is too much for her to expect from her life. Diana and Natalie reassure each other that they will “get by.” Natalie goes off to her dance.

Natalie finds Henry at the dance (“Hey #3 / Perfect for You (Reprise)”). She expresses her anxiety that she might be “crazy.” Henry promises to support her. Natalie worries that Henry will renege on his promise in several years, regretting his decision. Henry holds Natalie and reaffirms his promise to be a perfect partner for Natalie. They kiss.

Diana packs her belongings and informs Dan of her choice to leave home out of consideration for their mental health (“So Anyway”). While she is nervous about trying to deal with her mental illness by herself, she is reassured of the possibility that she can find a tenable solution on her own terms this way. Diana tells Dan that continuing to support her when it has produced no clear pathway towards resolution is not romantic. She acknowledges Dan’s love for her, but assures him that she needs to be on her own for the time being.

After Diana leaves, Dan privately acknowledges his identity as the person who supported and loved Diana to contrast it against Diana being the one who “walked away” from their relationship (“I Am the One (Reprise)”). The vision of Gabe approaches Dan, telling him that he’s always been present to support Dan, even though Dan never wanted to acknowledge his presence. Dan tries to push Gabe away, but Gabe insists that he won’t let go of Dan. Finally, Dan acknowledges Gabe’s presence, recalling the trauma of witnessing Gabe’s death and saying Gabe’s name for the first time.

The vision of Gabe vanishes as Natalie arrives home. Dan explains that Diana has left. Natalie observes that all the lights in the house are off and that they can’t rebuild their family life in the dark (“Light”). As Natalie begins turning on the lights, Dan acknowledges that they’ve waited too long for the light to enter their lives. Separately, Diana comments on the ambiguous path to survival, as well as the gratitude that comes with knowing she doesn’t have to be happy to be alive.

Some days later, Natalie tells Henry that Diana has moved back in with her parents, which she is skeptical about given that she has never found any consolation in going home. Henry reassures her that he will be there for her. Dan speaks to Doctor Madden to ask about Diana. Doctor Madden suggests that Diana is working on herself, but does not guarantee she will come home. He offers to refer Dan to a therapist, which Dan meekly accepts. Together, the characters, including Gabe, acknowledge their hope that the long dark path they are following will bring them to the light.