Nonnatus House may have lost Sister Evangelina (Pam Ferris) due to stroke, but the nursing convent will not be undermanned when "Call the Midwife" returns for its sixth season.

Radio Times revealed that veteran actress Dame Harriet Walter has been tapped to portray the role of Sister Ursula, the newest nun who will help Nonnatus House running. According to the 65-year-old actress, her character is "not a very welcome addition" to the group.

Walter appeared in several hit film and TV projects in the past, including "Star Wars: The Force Awakens," "Sense and Sensibility," "Atonement" and "Downton Abbey."

Meanwhile, writer Heidi Thomas teased what fans should expect when the period drama series returns on BBC.

"It's back to earth with a bump for our beloved midwives as they return from their magical Christmas mission trip to South Africa," Thomas told the publication. "It is now 1962, and in a rapidly changing world, the arrival of Sister Ursula – superbly played by Dame Harriet Walter – brings new challenges to Nonnatus House. Tears are shed, and bonds reinforced, as the team pull together as never before."

The returning cast for "Call the Midwife" season 6 includes Helen George as senior nurse Trixie Franklin, Charlotte Ritchie as midwife and nurse Barbara Gilbert, Emerald Fennell as nurse Patsy Mount, Jenny Agutter as the Nonnatus House's sister-in-charge Sister Julienne, Judy Parfitt as the retired midwife and nurse Sister Monica Joan. Meanwhile, actress Miranda Hart will reprise her role as Nurse Camilla Browne after leaving the show for a short hiatus for the special Christmas episode that will air this year.

The sixth season of "Call the Midwife" is expected to be launched sometime in 2017 on BBC One, but U.S. viewers should expect to hear an announcement about the show's premiere date on PBS in the coming days.