Fans of Outlander who know the books on which the Starz show is based know that one of the story’s most impactful deaths was quite different in the source material, and now the show’s producer Matthew B. Roberts is offering up some answers about why they made the change.

Needless to say, discussing character deaths will involve some big spoilers, so if you’re planning to watch the now concluded Outlander, be aware.

In the show, the character who dies is César Domboy’s Fergus, a close friend and ally of main character Jamie, who becomes a fixture in his life after a fateful encounter in Paris. However, in the original Outlander books, it’s Fergus’ son Henri-Christian who dies instead. According to Roberts, the switch all comes down to the needs of the story and the impact the death is meant to have on fans.

“For the television show, we know that the books are different and somebody else in the book dies. But in the television show, we just didn’t spend any time with that particular character who dies in the book,” Roberts said at a Paley Center event in honor of the series finale. “We spent a lot of time with Fergus, we care about him, we love him. And so the impact that it had on the story and the characters is what mattered for the television show, and that impact was massive for the family. It was massive for Jamie, it was massive for Claire, it had a huge impact, and then we could go somewhere with the story.”

“If it was Henri-Christian, it wouldn’t have impacted the family the same. Not that they didn’t love him, it’s just we only saw him in a couple episodes, and in the book you spend a lot more time with him, and so you get to know him more,” he adds. “And the reaction we got from the fans, the overall reaction of the whole fandom, was pretty amazing, that they felt the pain.”

Though Fergus’ death came as a shock to the characters and fans alike, César Domboy was fully prepared for his character’s death, and, according to Roberts, he was even excited about shooting the scene. As one might expect, the show’s producers also consulted Diana Gabaldon, the writer of the original Outlander novels.

“He was super excited. We said ‘We’re going down this path,’ and he was like, ‘Oh f–k yeah.’ He was just really excited about it. We vetted this. We talked to Diana and said ‘This is the path we want to go,’ and obviously if she said no, we wouldn’t have done it. But then we talked to César and said ‘We’re going to kill off your character.’ When we kill a character, we talk to the actor beforehand.”

Outlander’s series finale was released on May 15, concluding a run of eight seasons over 12 years. It tells the tale of a woman from the ’40s who is transported back to Scotland in the 1700s, becoming embroiled in a life of romance and intrigue with a man from the past.