Marcel took maternity leave in 2014 and Jac temporarily departs in the seventeenth series episode "Go the Distance", originally broadcast on 14 April 2015, after reuniting with Jonny Maconie (Michael Thomson).

[2] Marcel was introduced to the series alongside Luke Roberts and Tom Chambers, who portray cardiothoracic registrars Joseph Byrne and Sam Strachan, respectively.

[4] A writer from Inside Soap reported that Jac arrives at the hospital determined to impress consultant Ric Griffin (Hugh Quarshie).

[2] Though Jac rarely falls in love, she is not averse to using sexual manipulation to achieve her goals, for example she has had romances with several of her colleagues;[13][1] consultant Nick Jordan (Michael French), who she let "too close and was burned",[13] and foundation doctor Oliver Valentine (James Anderson).

Marcel told an Inside Soap reporter that Jac "finds it hard" because the evidence suggests she killed him, adding that "she has no credible alibi and her fingerprints are on the murder weapon.

[36] She soon covers for Faye to keep her secret hidden and takes the blame for a small fire ward sister Kyla Tyson (Rakie Ayola) causes.

[37] Then-script editor Simon Harper suggested pairing Jac with registrar Sacha Levy (Bob Barrett) following his introduction as the characters have contrasting personalities.

[41] Marcel and Barrett formed an idea that Jac and Sacha should live together in an unseen flat with viewers only seeing the characters speaking about home life.

Barrett dubbed Jac "Sacha's guardian angel" and she is saddened to hear about his battle, but is also "furious" that he did not speak to her or his former partner, Essie Harrison (Kaye Wragg).

"[30] Jac believes the only reason she secured a job at Holby City hospital is because she is an old friend of CEO Henrik Hanssen (Guy Henry).

[44] Rouass told Daniel Kilkelly of Digital Spy that while Jac and Sahira shared a "silent respect" over work, the characters are "completely different".

[46] Jac is under the impression that Jonny is a neurosurgeon, so she is surprised to learn that he is really a nurse and about to start working at Holby as part of the transplant team.

[49] Jac meets with her consultant obstetrician and gynaecologist Derwood Thompson (Ben Hull), who informs her that she has endometriosis, a condition which greatly reduces her chances of conceiving.

[51] Following Tara's funeral, Jac and Jonny have a one-night stand, but they both tell Mo Effanga (Chizzy Akudolu) separately that they do not plan on getting back together.

"[15] Jac immediately decides to make her junior doctors, Oliver and Zosia March (Camilla Arfwedson), prove themselves by handing them bad jobs.

"[65] Holby City series producer Kate Hall announced plans in August 2017 to pair Jac with director of nursing Adrian "Fletch" Fletcher (Alex Walkinshaw).

[66] She compared the matching to characters Maddie Hayes (Cybill Shepherd) and David Addison (Bruce Willis) in Moonlighting and Peter Joshua (Cary Grant) and Reggie Lampert (Audrey Hepburn) in Charade.

[68] Walkinshaw explained that this is refreshing for Jac as she is accustomed to "having a man standing opposite her desk, to attention, while she's sitting telling them off and letting them know exactly how the land lies.

Professor John Gaskell (Paul McGann) recommends that Jac takes part in his dodgy stem-cell treatment trial and he will perform the operation.

Jane Wallbank, the show's series producer, explained that Jac's professional and personal lives would place her under pressure, especially as she tries to prioritise her relationship with Emma (Darcey Burke).

[72][75] The actress received lots of encouragement from her agent and the producers, specifically Kate Oates, the Head of Continuing Drama at BBC Studios.

[75] One of Marcel's main concerns was that she would be putting her mental health at risk by portraying Jac's story, but decided that as long as she stayed healthy, she could do the plot "justice".

Having investigated the surgery, Elliot asks whether Jac is suffering with a mental health issue and also reveals that he is ill and in need of a high-risk operation.

[84] Advanced spoilers, released on 21 November 2019, revealed that Jac would receive treatment in a Psychiatric Unit, where she would be visited by Fletch, Sacha and Elliot, dubbed the "three wise men".

[96] The show's story producer Ben Wadey told Calli Kitson from Metro that writers were tasked with creating suitable endings for all the regular characters.

[102] As her condition deteriorates, Writers brought back the characters of Guy Self (John Michie) and Elliot Hope for the final part of Jac's story.

Executive producer Simon Harper explained that both casts would be featured "striving heroically against the odds in two episodes of pure, nail-biting, taut, emotional medical drama.

[121] For her portrayal of Jac, Marcel was nominated for Best Soap Actor (Female) at the 2018 Digital Spy Reader Awards; she came in seventh place with 6.4% of the total votes.

[39] Susanna Galton of the Daily Mirror called Jac an "uptight heart consultant" and a "frosty-faced, hard-as-nails doc who viewers have grown to love".

[126] Haasler (Metro) praised Marcel's "heartbreaking" acting and dubbed Jac's breakdown "a highly dramatic ending to what was a really gripping and, at times, difficult episode to watch.