The 34-year-old actress, who recently welcomed a son with husband Kit Harington], is to appear opposite "Divergent" actor Theo James on the upcoming HBO show, based on the Audrey Niffenegger novel of the same name.
The series, which has been in development since 2018, is described as an "intricate and magical love story that tells the story of Clare (Leslie) and Henry (James), and a marriage with a problem... time travel."
Leslie's character Clare has been described by HBO as "fiery, clever and unstoppable and for most of her life she's had an amazing secret. Since she was 6, she has had an imaginary friend: a kind and funny man, sometimes old, sometimes young, who appears in the woods behind her house and tells her tales of the future."
"Visits from the mysterious Henry are the bright spots in the tedium of her childhood. As the years pass, and she grows into a beautiful young woman, she starts to realize her friend is not imaginary - he's a time traveler, visiting from the future," the description continued. "And he's not just from any old future - he's from her future. Clare has a literal date with destiny."
Before landing this role on "The Time Traveler's Wife" series, the actress portraying Ygritte on "Game of Thrones" appeared in the first three seasons of "The Good Fight" opposite Christine Baranski. She has also played Gwen Dawson in several episodes of "Downton Abbey". Her future co-star, James, meanwhile has "Castlevania" and "Sanditon" in his TV credits.