The first trailer for Christmas episode of "Call the Midwife" was released on Monday.

In the first full trailer revealing a sneak peek into the BBC One special, Sister Monica Joan appears to be in trouble. The old, frazzled nun is seen walking through the forest while it's snowing seemingly searching for something.

There is also a scene where Sister Julienne is seen calling the authorities, while her and the other midwives appear worried.

Despite all the concerned looks in this trailer, there seems to be a few cheery moments, such as Fred wearing his Santa Suit for Father Christmas's annual trip to Poplar and Shelagh promising to put on a spectacular show for the local church. In this special episode, the people in Poplar also get ready to take a bus trip to see the Regent Street lights.

Along with Sister Monica Joan, who appears to have gone missing, mother Iris is also grieving due to the loss of her baby daughter.

The original show "Call the Midwife," which premiered Jan. 12, 2012, is based on the memoirs of Jennifer Worth, who was a district midwife in London's East End in the 1950s. Cast members on the show include Jenny Agutter, Pam Ferris, Miranda Hart, Judy Parfitt, Helen George, Bryony Hannah, Laura Main, Cliff Parisi, Charlotte Ritchie and Linda Bassett.

There will be a fifth season, including eight episodes, of "Call the Midwife" airing on BBC One in early 2016. BBC has also ordered another special episode of the show for 2016. A sixth season has also been ordered of the show and is set for 2017. The show also airs on PBS in the U.S. 

"Call the Midwife" recently won for Best Family Drama at the U.K. TV Choice Awards. Hart also won in 2013 for Best Actress at the same awards show, while the show itself was nominated for Best Drama Series.

The Christmas special will air on PBS on Christmas Day at 9 p.m. ET. The show's fifth season will return in Spring 2016.