A few months after her arrival, it emerges that Sam is married to fellow ED doctor Dylan Keogh (William Beck).
The couple's relationship is tested by her friendship with Iain Dean (Michael Stevenson), but they later marry and make their last appearances in twenty-eighth series episode "Away in a Manger", which aired on 14 December 2013.
When Salt wanted to leave the show once more, producers decided to kill her character off, and Sam's final scenes aired in episode 1094, broadcast on 18 August 2018.
On 30 September 2011, the BBC announced actress Charlotte Salt had joined the cast of Casualty as "ambitious army medic" Sam Nicholls.
[1] Series producer at the time, Nikki Wilson, commented that the character would be exciting and intriguing when she made her debut in October.
Before coming to Holby, Sam was an army medic who served in Afghanistan – where she thrived on the adrenaline rush of combat medicine.
"[5] She told Patrick McLennan of What's on TV that Sam was a tough, "action girl", who was keen to save everyone, but she did not want her to seem like a "war machine".
Salt stated that Sam would find it hard to adapt to working at Holby, after being in a war zone, and that she would be haunted by her time over there.
"[2] Sam turns up to work at the hospital a day early, and decides to go out with paramedics Dixie Dixon (Jane Hazlegrove) and Jeff Collier (Matt Bardock).
Salt told Katy Moon of Inside Soap that Sam approaches the scene "in true Army style" which annoys Dixie and Jeff.
[7] As they descend into the cave, Sam and Dylan try to keep their relationship professional, but soon begin to argue about their failed marriage, placing themselves and their patients in danger.
[7] Speaking to Sarah Ellis of Inside Soap, Salt said that being trapped in the cave with Dylan was Sam's "worst nightmare" and that the situation caused all of the issues about their marriage to come to a head.
[10] One of the character's more notable storyline arcs began in early 2012 when Sam saves Dylan from being attacked by patient Keith Parr (Marshall Lancaster).
[11] Salt explained to Sarah Ellis of Inside Soap that when Sam see Dylan's life under threat, her first thought is to protect him.
[11] Producer Nikki Harris said the storyline would "bubble under for the rest of the series" and would raise the issue of whether Sam used excessive force.
[12] Keen to avoid having legal action brought against the hospital, Zoe Hanna asks Sam to meet with Keith and apologise.
[13] A lawyer for the General Medical Council investigates Keith's complaint and Sam's colleagues are asked to give statements about the incident.
[14] In March 2012, Daniel Kilkelly of Digital Spy reported a special Red Button episode titled "Under Fire" would explore Sam's time in Afghanistan, and the events that led to her arrival at Holby.
[15] Producers told Kilkelly that the episode would explain Sam's "brusque bedside manner and brave but impulsive decision-making".
[15] The episode is set in Camp Bastion and explores Sam's time working on a MERT helicopter, alongside Corporal Iain Dean (Michael Stevenson), who she is having an affair with.
[21] Sam worries that Tom is only making their relationship official because someone else in interested in her, but he assures her that he is serious and they put on a public display of affection in front of their colleagues.
He tries to keep his plans a secret, but nurse Robyn Miller (Amanda Henderson) sees Tom showing off the ring to a patient, and soon everyone in the ED knows.
[24] Salt told Inside Soap's Katy Moon, "Sam realises that she doesn't have to be a tough girl on her own any more – it's a real turning point.
"[24] During a February 2017 interview with Sophie Dainty of Digital Spy, producer Erika Hossington confirmed that a previous love interest of Dylan's would be returning.
"[29] Salt called Sam's first shout "a heavy one" to film, as the weather was bad and she had take part in a large medical procedure.
[29] When asked by Sarah Ellis of Inside Soap what had happened between Sam and Tom, Salt replied that there would be hints that their marriage had "fallen apart", but nothing else would be said.
[29] Salt added that Dylan would be surprised to learn that Sam is back and single again, while her presence would also cause trouble between Iain and his new partner Lily Chao (Crystal Yu).
When she was informed that her character would die, Salt admitted that she was shocked, but she wanted Sam to leave during a big storyline, as she was not planning on returning again.
[31] The actress said, "They wanted to create a really lovely, dramatic exit for me to leave on and this opportunity arose when they planned this huge motorway pile-up.
[32] Of Sam's introduction, David Butcher of the Radio Times commented, "From the word go, she makes her presence felt with 'tools civilians can only dream about'.