Arrow has signed a new deal for four books from saga writer Donna Douglas.
Publishing director Jenny Geras bought world English rights to the books from Caroline Sheldon at the Caroline Sheldon Literary Agency.
Douglas has previously written the Nightingale Nurses series for Arrow, which is set in The Nightingale Hospital in London’s East End in the 1930s.
The first book in the new contract will be published in May 2015, and Arrow will release two books a year – one in spring and one in autumn.
Geras said: “We are thrilled to have Donna signed up for four more books. The Nightingales series has got off to the most fantastic start and has proved an immediate hit with all those fans of Call the Midwife.
“The first two books in this new series will move the nurses into the Second World War.”