What did Tully do to Kate that was so unforgivable in Firefly Lane?

You’d be excused not to remember exactly what happened in the first season of Netflix hit Firefly Lane. After all, the first episodes of the series were released nearly two years ago. 

But as Firefly Lane season 2 is about to drop, star Katherine Heigl has gone on the record about the most salacious question involving the show's plot: what did Tully do to Kate that was so unforgivable?

The good news is that we will, indeed, have an answer to our query as the new episodes air. 

"Yes, you will learn," Katherine, who plays Tully, said to TODAY. "These first nine [episodes] that are going to drop, you will discover what it is that has really fractured that relationship. It's pretty big, it's pretty juicy."

As a reminder, in the season one finale, audience members were shocked to witness Kate, played by Sarah Chalke, asking her best friend Tully to stay away from her father's funeral. 

"When I said that I could never forgive you for what you did, what did you think that meant?," the character is heard saying to her former pal. "Go home. Now. I don't ever want to see you again."

Sarah herself went on the record about the rift in a season two announcement video - but the actor didn't disclose too many details. "This issue between Tully and Kate: we can't say much," she noted. "But we can say that it's family-related and has nothing to do with Johnny."

Johnny, played by Ben Lawson, is, of course, Kate's soon-to-be ex-husband. As a reminder, Johnny and Tully did share a romantic connection while younger. But, alas, although plenty of fans always thought that the friendship breakup was due to the past fling, Sarah basically confirmed that not to be the case.

Given the fact that the show is based on the Firefly Lane book by Kristin Hannah, plenty of people have turned to the literary inspiration for some clues regarding what happened between the two friends. Spoiler alert: in the novel, a big fight breaks out between Tully, a famous talk show host, and Kate after the journalist brings her friend and her daughter Marah on the show. Does Tully embarrass them on the air? Does she, perhaps, disclose sensitive details about their private lives to her many viewers?

We’ll have to wait and see what kind of situation will unfold on the small screen when the first nine episodes of the series drop on Netflix. Fair warning, though - the entire season won't be available at once. The remaining seven episodes will air sometime in 2023. 

Speaking of the new episodes, fans can expect a slew of new actors to populate the show including Jolene Purdy of The White Lotus fame, who will play Justine Jordan, an upbeat talent agent, Greg Germann as scion Benedict Binswanger, Ignacio Serricchio taking on the role of cocky sportscaster Danny Diaz and India de Beaufort as reporter Charlotte.