There will be spoilers from Diana Gabaldon's books throughout this story!
A lot has occurred during the first two seasons of Outlander, both in Claire's life with Jamie and her life with her original husband Frank. When Claire returned from the time of the Jacobite Rebellion and was pregnant with another man's baby, Frank stuck around, but he never really wanted to hear about time travel or understand Claire's perspective. Sticking around sometimes isn't enough, and series lead Caitriona Balfe recently revealed in an interview that Frank and Claire's marriage is totally doomed. Here's what she had to say.
At this point in Claire's life, Jamie's dead. She's trying to build a life after him, but once you've experienced a love so all-consuming, nothing can live up to it. Claire decides to focus on her career and tries to slot Frank in. That leads to disappointment and resentment. It's a broken marriage.
We've known for a while that Tobias Menzies would continue to be a part of Outlander during Season 3, and while this could mean we'd see Black Jack Randall, at the time it was mentioned we were going to learn more about Claire and Frank's post-return relationship, a relationship we only saw snippets of during Season 2. Of course, we know from scenes like the one in which Brianna blamed her mother for her parents' issues that the two didn't get along for most of Brianna's life, but clearly the relationship is a lot more complicated than that. From what Caitriona Balfe is saying to TV Insider, it won't be just time travel coming between the couple, but nonetheless, Claire's love for Jamie will build walls between them. Her life with Frank won't always be the happiest life.
Although the third book in the series, Voyager, shares a lot about Jamie's life post-Culloden, we will get to learn more about the older, wiser Claire too. We should see her study to become a doctor, which is alluded to in the above quote and also in the casting of Dr. Joe Abernathy, who is Claire's friend in medical school. We did originally learn there was tension between Frank and Claire in Season 2, but it should be much harder to see Claire distance herself from her original husband as time passes.
Outlander has done a great job so far with its time hopping, which has shown us characters like Jamie, Claire and Brianna in different time periods of their lives. The show hops back and forth quite frequently, but we always get the information we've needed at the time. Ultimately, we know that Claire now knows Jamie did not die as a young man. The last scene in Season 2 indicated that she will attempt to return to him and we can't wait to see what happens when she does.