In Outlander season 7, episode 4, Brianna and Roger found themselves grappling with the lies of their son, Jemmy. It was a struggle for them to understand why he kept talking about mythical Scottish creatures, especially when neither Roger nor Jamie had ever discussed these folklores with him. Jemmy's vivid imagination always led him to believe that what he said was true, and this often left his parents and grandparents puzzled.

Jemmy's ability to time travel was apparent in his knowledge that his sister, Mandy, possessed the same power.

This knowledge made Jemmy an important figure in ensuring the Mackenzie family's journey to a future that could have potentially helped Mandy. However, Jemmy's deceptive behavior, such as pretending to have broken the radio, made it difficult for Roger and Brianna to trust him when he spoke of the Nuckelavees.

Interestingly, the book An Echo in the Bone reveals that Jemmy's claims about Nuckelavees find their roots in the character of Buck Mackenzie, who Roger is a descendant of. Buck, the illegitimate son of Geillis Duncan and Dougal Mackenzie, inherited the power of time travel from his mother.

After accidentally being transported 200 years into the future, Buck found himself relying on Roger, who was the only person he knew in this unfamiliar time period.

Despite their complicated past, Buck and Roger formed an unexpected alliance. Using Scottish folklore as a way to persuade Jemmy to help him, Buck aimed to survive in this strange era. Their collaboration not only allows Roger to experience time travel once again but also introduces another time traveler, Jeremiah Walter Mackenzie, who is Roger's father. Together, they navigate through challenges, save Jerry Mackenzie, and encounter significant characters from Claire and Jamie's past.