It wouldn't be Christmas without the Call The Midwife special and now we have first look images of the upcoming spin-off after filming wrapped. Call The Midwife: Sisters In Arms will be a prequel to the original BBC series, set in Poplar in September 1939 during the outbreak of the Second World War. 'But I was surprised how many new emotions Call The Midwife: Sisters In Arms sparked. Call The Midwife, which follows the group of nurse midwives working in east London through the decades, began in January 2012 and has had 15 series, with each featuring a Christmas special. Sister Alice and Helena Wilson as Sister Julienne with a clapperboard at the end of filming for the three-part special, Call the Midwife: Sisters in Arms.