For the penultimate episode of Outlander, the Starz series turned to the definitive voice of Jamie and Claire — Outlander author Diana Gabaldon. She penned “Pharos,” which saw Jamie, Claire, and William team up to save Lord John Grey. The author and show consultant spoke to DECIDER about the process of writing the TV script, whether or not this episode gives away anything from her forthcoming Book 10, and what to expect from the highly anticipated series finale.

For “Pharos,” similar to when she has written other Outlander episodes — Season 2’s “Vengeance is Mine,” Season 5’s “Journeycake,” and Season 7’s “Ye Dinna Get Used to It Ye Dinna Get Used to It” — Gabaldon worked from an outline that was put together by the producers, including showrunner Matthew B. Roberts; the production staff; and the writers’ room.

“I wrote the script pretty much according to their outline, and included some specific things that I thought would work,” she says. “Shaping the script is pretty much in my hands entirely. The total content, only up to a point.”

“Sometimes I invent something. The idea of Jamie and William diving in and swimming up into the boat shed was mine,” Gabaldon says, referencing the father and son’s very Apocalypse Now-like entrance from the water when they arrive to save Lord John. “It’s just the sort of thing they would do,” she says.

Another idea of hers was the lighthouse being the clue on how the trio found Lord John, when he carved the Greek word for lighthouse, “Pharos,” into his ring. “Most of a lot of the other stuff was there [in the outline],” she says. “And [the show writers] really don’t care as long as it results in a good script overall.”

For those who have read the books by Gabaldon, they’ll know that the ninth book, Go Tell the Bees That I Am Gone, ends with William coming to Fraser’s Ridge asking Jamie for help to find Lord John. So the events of both Episodes 808 (“In The Forest”) and 809 haven’t occurred in the books. Meanwhile, the battle of Kings Mountain, which will take place in the grand finale episode of Outlander (where Jamie could possibly die!), already happened in Book 9. But the author says that doesn’t mean that the events of “Pharos” are major spoilers for Gabaldon’s forthcoming final tenth book in the Jamie and Claire story, A Blessing for a Warrior Going Out.

“It’s completely separate,” Gabaldon says of the TV story and her books. “They’re all deviations from the timeline because you have to just rearrange all of the information you have from the book, and what information you use. To a TV writer, [the books’] timelines mean nothing. So they will happily pick up an incident here and stuff it in some two years earlier, so yes, stuff in here does happen before Kings Mountain in the show.”

There have been quite a few notable changes from the source material in Season 8. And Gabaldon has already been vocal about the changes that took place in Episode 807 (“Evidence of Things Not Seen”) which caused quite a stir within the fandom due to Fergus’ death and the confirmation that Faith survived birth. “I’m not going to say anything else,” she says with a laugh. 

Although she had strong feelings about those particular changes, for the most part, she takes the show’s divergences in stride. “It’s definitely not the way it is in the book, but it never is,” she says. “It’s an adaptation, and you just can’t pour an 80-pound book into a 10-ounce TV show. That’s what it amounts to.”

But some elements are the same in both the book and the show. For instance, Ezekiel Richardson’s motivation for kidnapping Lord John in “Pharos” is the same as in Bees (though in the book, he confesses it to Lord John rather than to Claire). But the details are the same — he’s a time traveler from the future who wants to end slavery in the U.S. and thinks the best way to do it is to have the British win the American Revolutionary War. (As for whether book readers should believe Richardson, Gabaldon says, “Oh, sure, for lack of anything better to believe.”) He thinks that stopping Hal Grey from giving a speech about pulling war funding is the key, thus blackmailing his brother, Lord John.

Because of these plot similarities, readers may be inclined to think that how Lord John’s kidnapping plot is resolved in the show — with Lord John shooting Richardson after Claire has decided to let him go — happens in Book 10. But Gabaldon again advises against that, “No, you should never, never take anything the show says as something that’s going to happen in a future book.” Though she admits, “Occasionally, it does. I do talk to [production] about what’s going to happen in future parts of the book.”

The other major death in the episode — Percy Beauchamp Wainwright — already happened in the book. In Bees, Percy presumably died in Bees by drinking poisoned brandy when telling William about Lord John Grey’s capture. It’s not 100% certain if his death was an accident or if he’s even truly dead in the books. But Gabaldon confirms the show writers wanted a definitive end to Percy’s TV story. “They wanted to get rid of him, not leave him as a loose end.”

So after betraying him to Richardson and exposing their sexual relationship, Lord John gives Percy the choice to sign an affidavit saying his testimony about his confession was a lie, leading him to go to prison, or… die. Neither is an ideal option for the cowardly Percy. In the end, he does both. He signs the affidavit, protecting Lord John from any future blackmail using his sexuality against him, and then he shoots himself. 

Gabaldon admits she doesn’t find Percy’s TV death to be super true to his book counterpart. “I said to myself, as anybody who’s been reading the books would likely realize, that Percy is much too selfish to ever commit suicide,” she says. “I think that in my original draft of the script, Richardson shot him rather than him committing suicide. But then they decided that’s not going to work for other reasons.”

Other moments that came from the TV writers include the big emotional lookback Jamie gives to William when leaving Savannah after safely reuniting him with his adoptive father. Back in Season 3, Jamie hadn’t looked back at the child William when he left him, something William confronted Jamie about in Episode 808, “In the Forest.”

“I don’t think that I wrote that in,” she says of Jamie looking back. But she says she approved of the handling of Jamie and William’s relationship in Episode 808 from original showrunner Ronald D. Moore. “The apparent motive there was to absolve Jamie for deliberately deserting William at Helwater, which is how William sees it, of course, having not realized at the time what was up.”

“I thought everything between William and Jamie worked really well.” But as she notes, “In terms of the book, William wasn’t there [at Fraser’s Ridge].” So readers will have to wait to see how she handles the father-son reconciliation in Book 10.

With Jamie giving William the look he didn’t give him back in Season 3’s “Of Lost Things,” it felt like a fitting end to William’s TV story (bonus: he broke up with the slightly sketchy Amaranthus). And Gabaldon notes that viewers probably shouldn’t expect to see William or Lord John again in Outlander. “I think that that’s probably it,” she says. “I think we’ve seen the last of them. I don’t swear to it, because Lord John might pop up somewhere else, but I’m pretty sure that William is done.”

Could David Berry’s Lord John also pop up in another Starz series? Perhaps the long-rumored spinoff based on Gabaldon’s Lord John novellas? “Well, things like that would probably depend to a large extent on how successful Blood of My Blood is,” Gabaldon says of the other Outlander spinoff, which will return for a Season 2 sometime in the fall. “Beyond that, I couldn’t tell you anything for sure.”

And lest fans forget, “Pharos” even has a little reference to Blood of My Blood. When talking to William about having two fathers, Claire rather uncharacteristically brought up her own father, Henry. “That’s definitely what it was,” Gabladon says of the tie-in. “That’s just a little thread reminding us about Henry and Julia.” But there probably won’t be any other nods to the prequel series in the Outlander finale.

As for the series finale, there was a clue to how it could all wrap up toward the end of “Pharos.” Jamie interrupts Claire while she’s writing in her journal. But instead of her drawing “wee beasties,” her time with Richardson apparently inspired her to muse about time travel. “People disappear all the time…” Jamie reads, with Claire’s words coming directly from the opening lines of the very first Outlander episode and book.

That heavily implies that Outlander has been Claire’s telling of her and Jamie’s story the whole time. Maybe that’s why the show made sure to incorporate Claire’s voiceover in the penultimate episode, since Gabaldon confirms the voiceover was a directive from the TV writers and not an idea of hers.

Gabaldon says Claire’s writing will come into play in the series finale. “That’s something just for the show. You’ll see why when you see the last episode,” she says. “There’s a purely cinematic reason for that, which will appear … but that’s definitely not in the book.”

As for any other tidbits about the series finale, Gabaldon obviously can’t say much. “The final episode is largely about Kings Mountain,” she says. “Not entirely. There’s part of it that happens on the Ridge.” 

Roberts wrote the finale, but she says she also contributed to the script, and the title, “And the World Was All Around Us,” comes from the last line of her original Outlander book. What she can confirm is that the ending to Jamie and Claire’s story is not open-ended. “It’s definitive,” she says. “I thought they should not leave any loopholes because it is the end of the season and they’re not getting another one, so there’s no point in leaving open possibilities…. well, not leaving many possibilities open. There’s always some that are going to exist.”

“[Roberts] and I agreed that it should just end very conclusively. And what he did … works effectively.”

Gabaldon says she’ll be watching the finale when it airs on Friday, May 15, from her home in Scottsdale, Ariz. Though this monumental farewell won’t stop her from her dinner plans. “If it happens at dinnertime, I’ll have to wait and watch it later in the evening.” But she’s excited to hear the fans’ reactions. “It will be great.”

And don’t fret, book readers — the ending of the Starz show doesn’t mean the ending of A Blessing for a Warrior Going Out is spoiled. “It doesn’t happen that way in the book. The book has a completely separate ending,” she confirms. You heard it here from Herself.

Caitlin Gallagher is a New Jersey-raised, NYC-based entertainment writer. When not writing about or watching TV, she can be found planning her next Halloween costume, crying over rescue animals, or praising Season 2 of The Leftovers.