After the cast for the show's fourth series was announced, and Aldridge's absence was quickly noted, it was confirmed that he had left the role to pursue other projects he had commitments to.

He initially doubts the capabilities of the team's new medic, Molly Dawes (Lacey Turner), but learns to respect her after she saves the life of fellow soldier Smurf (Iwan Rheon) in an act of bravery.

Despite Captain James telling her not to, Molly befriends a local girl named Bashira (Becky Eggersglusz), who warns her not to let 2-Section go to a mountain checkpoint, proving to be vital information which impresses him.

After marrying Molly, Captain James offers Lance Corporal Georgie Lane (Michelle Keegan), an experienced army medic, a place on a humanitarian mission in Kenya with 2-Section, which she accepts.

A unit arrives, and Captain James is shocked to see it being led by his old friend Elvis Harte (Luke Pasqualino), who is also Georgie's ex-fiancé who abandoned her on their wedding day.

After an earthquake in Nepal, 2-Section is deployed on a humanitarian mission there, and Captain James arranges for Georgie to mentor new recruit Maisie Richards (Shalom Brune-Franklin).

He cheers up when he meets Captain Azizi (Jonas Khan) again, who asks him to abort the mission out of fear of how the British Army's presence impacts Afghanistan's terrorism.

After being cast in Our Girl, actor Ben Aldridge described his character as "an interesting mix of authority and fun" and someone who has an occasionally "laissez-faire" attitude towards leadership.

[1] Captain James would feature in a love triangle with protagonist Molly Dawes (Lacey Turner) and his friend Smurf (Iwan Rheon).

[6] Set to follow 2-Section through a humanitarian mission in Kenya, Captain James would ask new lead Georgie Lane (Michelle Keegan) to join the team.

Explaining the offer, Aldridge commented that the team "needs an experienced and trustworthy medic" following Molly's departure and knows Georgie is "more than capable".

[6] When series three was greenlit, Aldridge teased that it would see Captain James "trying to lose himself in his work" as a method of remaining strong after Elvis's death, noting he was "quietly grieving" underneath.

[7] The actor added that the ambiguity of how responsible he was for Elvis's death haunted Captain James throughout the series and would see him beginning to question if a future in the British Army was a good idea for his mental health.

[7] When asked how his character's marriage to Molly was going, Aldridge teased bad news for the pair, as constantly being apart would begin to put strain on the relationship.

[10] Grounds assured audiences that Captain James survived a cliffhanger at the end of series three and had returned home to work on his marriage to Molly, which Georgie supported him on.

[13] Justin Harp of Digital Spy reported negative reactions to the episode broadcast on 26 June 2018, which showed Captain James admit his infatuation with Georgie.

[15] Suzanna Lazarus of Radio Times opined that the episode put Captain James through "quite an ordeal" and called a leg injury he sustained in it "gruesome".

[8] When it was announced that Aldridge had left the series, Lazarus's colleague Ben Allen voiced disappointment that the relationship plot line would be abruptly ended, calling it "anticlimactic".