Warning: Spoilers for Firefly Lane season 1 and the novel on which its based are ahead.
For several episodes, the flash forwards to the funeral in Firefly Lane seem to suggest that Tully Hart (Katherine Heigl) may have died. By the end of the season, viewers learn the truth — Kate Mularkey's (Sarah Chalke) dad is the one who died. Kate and Tully's friendship is also seemingly dead. The two haven't talked since some unnamed incident, and Kate isn't ready to make up with Tully during those 2005-era scenes. But the funeral also serves to foreshadow another death that book readers know is coming.
In the book, written by Kristin Hannah, Kate is diagnosed with inflammatory breast cancer and ultimately passes away in 2006 — only a year after Tully and Kate face off at Kate's dad's funeral on the show. But before Kate's death, her illness helps Kate and Tully reconcile in the novel. The two had a falling out after Kate felt that Tully ambushed her during a segment on Tully's show. Tully, in an attempt to help Kate and her daughter work on their relationship, ended up making Kate feel like a bad mother. Kate got angry and cut off contact with Tully, and Tully's stubbornness didn't allow her to make the first move to apologize.
However, once Kate gets sick, she reaches out to her old friend, and Tully initially ignores her call. But months later, after all the treatments and trials have failed and Kate knows that she's at the end of things, she tries again. She calls and tells Tully that she's in the hospital. Suddenly their fight melts away, and the friendship that was always there underneath takes its place. Tully rushes to be by Kate's side, and the two of them tackle Kate's final months together. When faced with the idea of Kate dying, neither of them want to hold onto old grudges. "When you get to the end, you see that love and family are all there is. Nothing else matters," Kate tells Tully, who replies, "You're my family, Katie."
Kate's breast cancer storyline was very personal for author Kristin Hannah, who lost her mother to the same illness. In an afterword in the novel, Hannah wrote that she hopes the story encourages women to stay on top of their health and pay attention to potential warning signs. "If something feels wrong, don't be afraid to ask questions or get second opinions. We women know our bodies; we know when something doesn't feel or look right," Hannah wrote. "I know it can be scary and difficult, but fear is no excuse to turn away. If you find yourself hesitating, or giving in to your fear, look to a friend for help and support. That’s the best thing about being a woman — we're always there for each other. As Tully and Kate would say: no matter what."
Ultimately, the book ends shortly after Kate passes, and Tully discovers that Kate left one last gift behind — a box of treasures and memories from their life together, including an iPod (it's 2006, iPods are still a thing) with the song "Dancing Queen" on it. The novel closes with Tully dancing to the song like she and Kate did when they were just teenagers first meeting in the '70s.
But while the novel ends with Kate's death, that's not to say a second season of the Netflix series would play out the same story. Until Netflix officially renews the show and we get our eyes on those episodes, we can mull over the book's heartfelt ending.