The clip suggests that viewers are in for an emotional rollercoaster this Christmas.
Outside Christmas spirit fills the air, with a jovial Father Christmas waving from the back of a Routemaster bus, and Christmas trees and lights adorning the streets.
In the local church, cameras role as the BBC comes to Poplar to record a carol concert. New-face Adrian Scarborough (The King’s Speech, Miranda) can be seen in earnest talks with Shelagh Turner (Laura Main) who promises him a show to be proud of.
However at Nonnatus House Christmas is yet to come.
The Sisters look worried, there are no decorations up, and elderly Sister Monica Joan (Judy Parfitt) is shown looking lost, and staggering alone through the bitter winter as snowflakes twist around her.
Call the Midwife is back on Christmas Day at 7.30pm on BBC One
Picture courtesy of BBC/Neal Street Productions