Call the Midwife’s Nurse Trixie will still be struggling with alcoholism and series seven will feature "painful" storylines for the popular character.
Helen George’s character, who has been on the hit BBC period drama since series one, is currently in a happy relationship with dentist Christopher (Jack Hawkins).
However, the path of true love won’t run smooth for Trixie in series seven and the show will revisit her demons and battle with drink.
"A lot of Trixie's glamour, her beauty, her fashion sense, it's all to do with covering up the very fragile woman she is inside,” said creator Heidi Thomas.
"We've had hugely positive feedback from the AA community in particular about her sobriety, and we liaise with the AA about her journey."
Thomas added: “In series seven we decided it was time to challenge Trixie, as we felt it wouldn't be realistic if she never stumbled on that path, and Helen once again gives a tour de force performance in the role.
“We discover something a little more about Trixie, about her hunger for love and how even though she's met this gorgeous, funny, respectable dentist, he comes with baggage. The path of true love doesn't run as smoothly as we would like and that's very painful for Trixie.”
Helen George revealed that Trixie’s relationship with Christopher will be put under pressure from his desire for sex before marriage and also his previous marriage.
"It’s quite interesting as he puts a little pressure on her to spend her first night with him, which really brings up the idea of contraception," said George.
"She confides in him quite a lot about her drinking and he’s there for her as support outside of Nonnatus House. The only problem with their relationship is that he has an ex-wife, with whom he shares a child, who isn’t necessarily happy that Christopher is seeing a new women. His daughter Alexandra is lovely little girl who Trixie really takes to and they have quite a strong bond."
Speaking about Trixie’s alcoholism storyline, George added: "At the start of the series, Trixie is still sober and going strong with her AA meetings. We take a glimpse into one of her meetings, and it’s good to revisit that so we see that Trixie has this ongoing struggle with alcohol and it’s not fixed, it’s not solved.
"And you really hear her share and you hear how much time Trixie actually spends on this, how much time she spends going to AA meetings, but more importantly how much she thinks about drinking, or rather not drinking. Drink’s always on her mind and you really get to grips with her struggle and how at the forefront of her thoughts it still is, even though you see her not drinking, it’s still there."
Call the Midwife returns for its seventh season on Sunday, January 21st at 8pm on BBC One.
Never miss an episode with BT TV – catch up via the BBC iPlayer app.