Call the Midwife returns with more compelling stories from the nurses and nuns of Nonnatus House. This season Sister Monica Joan goes missing at Christmas time leaving the nuns and nurses distraught. Shelagh rushes to put together a children’s choir in time for a BBC broadcast from the church. Elsewhere Trixie, having battled through her issues with alcohol, finds a new purpose in her keep fit classes. And could friendship blossom into something more for vicar Tom Hereward and Barbara?