There are a few people who should know that Claire is a time traveler in Outlander. Fergus is one of them, but has he found out?
In the TV show, it’s pretty clear that Fergus and Marsali don’t know that Claire is a time traveler. At least, by Outlander Season 5, Marsali doesn’t know. She asks Claire if Claire is a witch when it comes to doing autopsies. Why would Marsali ask this if she knew the truth?
It also doesn’t seem like Fergus knows. When talking to Claire about dwarves in Outlander Season 6, Fergus shares his experience. He doesn’t ask how things change in the future, which he probably would think about if he knew about time travel.
That’s the show. What about the books? Does Fergus know the truth in the Outlander books?
Fergus apparently knows Claire is a time traveler in Outlander
Diana Gabaldon mentions now and then on social media that Fergus knows Claire is a time traveler. This is something that happens off-book in the series. Fergus and Marsali have both learned the truth, which is important for later books.
In Written in My Own Heart’s Blood, there is a moment where Claire and Jamie are talking about taking Germain back to the Ridge with them. Jamie notes that Claire has told Fergus and Marsali about when the Revolutionary War will come to an end. She’d need to have told them she’s a time traveler to be able to explain that one.
Jenny does eventually find out. In fact, the Murray family at Lallybroch find out the truth. It would be a little odd if Jenny learned the truth but Fergus and Marsali didn’t.
This doesn’t mean Fergus and Marsali would have to accept it. They could view Claire as some sort of otherworldly figure, but it does look like they know something in the Outlander books.