“Outlander” Season 2 has kept fans guessing. Even the readers of Diana Gabaldon’s novels didn’t see the twist in episode 11 coming. The Starz drama killed off Duke of Sandringham in an unexpected way, and deviations from the source material may have shocked viewers who knew Gabaldon wrote Saturday’s episode. Executive producer Ronald D. Moore revealed why those changes had to be made.

“Some of it was just physical logistics in terms of our sets and choices of where we wanted everybody to be,” Moore told the Hollywood Reporter. “In the book, the death of the duke happened off camera. Murtagh [Duncan Lacroix] left them and came back with just the head in the bag and presented it to Claire [Caitriona Balfe]. We just thought that, for TV, that wasn’t going to be dramatically satisfying. You wanted to see it happen.”

“Outlander” fans are beginning to realize the books can’t prepare them for all the surprises in the time-travel drama. In episode 10, Angus (Stephen Walters) died, even though he was not killed in the books. Still, Simon Callow, who played the Duke of Sandringham, was not expecting to be gruesomely beheaded. “I thought I knew that he was going to die at the battle of Culloden, but I certainly didn’t know he was going to die the way he did die. It’s a very satisfactory way to die,” the actor told TVLine.

The sequence got even bloodier when Mary (Rosie Day) stabbed her rapist, something that didn’t happen in the book, “Dragonfly in Amber.” Jamie (Sam Heughan) slits the rapist’s throat in the novel. Moore explained that Mary’s storyline fit well within the episode and achieves the same goals that it does in the books. It just happens in a different way.

“It’s illustrative of how we design the show,” Moore said. “We’re trying to get to a story point that the book has laid out for us, but we changed it because we want to play it on camera instead of off, but it has to occur at a certain moment since it’s the climax, and so we should make that the climax of Mary’s story, too. So as we start filling in these requirements, you can see why we start bending the stories in certain ways, even though the intention is still to do the same version that the book does.”

Gabaldon warned fans before the episode aired that there would be some changes and said she was happy with her first script. “So, no — what you’re going to see is not Just The Way It Is In The Book, nor is every word exactly the way I wrote it,” she wrote on Facebook. “I think it is pretty good, though, and trust you’ll enjoy it when you see it.”

“Outlander” Season 2 airs on Starz Saturdays at 9 p.m. EDT.