Much-hyped ITV drama A Confession details the disappearance of 22-year-old Sian O’Callaghan who days later was discovered brutally burdered.
On a night out with friends in March 2011, Sian left a nightclub to walk the 800 metres home to boyfriend Kevin Reape but never made it there.
The evening had been a rare treat for Sian, who had been saving up for weeks for a New York trip with Kevin.
It was Kevin, played in the series by This Country's Charlie Cooper, who rang the alarm when Sian failed to return home that night, reporting her missing to the police at 9:45am after she failed to respond to a series of increasingly frantic text messages.
A public appeal was launched for Sian's whereabouts and a search for the missing 22-year-old soon commenced.
Her mobile phone was traced to Savernake Forest, some 12 miles from the club she had been at with friends.
The last message, registered with a phone mast there, was sent by boyfriend Kevin at 3.24am.
Detective Superintendent Steve Fulcher, played by Martin Freeman in the ITV series, headed up the investigation into Sian's disapearance.
Days after he reported Sian missing, her boyfriend Kevin was called in to Gablecross Police Station, Swindon, for a chat with Fulcher.
"I wanted to look Kevin in the eye myself and know for my own peace of mind that those instinctive alarm bells inside every copper didn't jingle one iota," Fulcher later explained.
Kevin, 25 at the time, volunteered to go to the Swindon station and willingly surrendered his mobile phone and key to his house to help with enquiries.
His phone, Facebook account and computer would all undergo a check too, Fulcher claimed.
Speaking in his 2017 biography, Catching a Serial Killer: My hunt for murderer Christopher Halliwell, Fulcher said: "It was imperative that we bottomed this out," - adding that his main aim of the meeting was to test Kevin's alibi and find out if he could be lying.
Fulcher said: "If you were the boyfriend in a missing-person case being spoken to by a detective, and you knew from watching TV crime shows that you were probably favourite, how would you react?
"So I took Kevin's pale complexion with a pinch of salt, and the same went for his anxious manner."
He went on: "The meeting with Kevin - despite its intensity - was run along the lines of fluid conversation rather than interrogation. I knew only too well that if you went in hard and oppressive, suspects clammed up and gave you nothing."
But it was during the 'intense' hour long meeting that Fulcher realised Kevin was telling the truth about his adoration of Sian and how he was a 'genuinely nice guy caught up in a nightmare.'
"He answered everything I asked him very fully and gave me every impression that he was eager to help. I could see that he was clearly in a very loving relationship with Sian and was devastated by her disappearance," said Fulcher. "As far as he was concerned, she was his lifetime partner; a likely future wife."
Fulcher said it was Kevin's heartache that gave him a 'renewed passion' to find Sian as quickly as possible.
Five days after Kevin first reported Sian missing, her body was found and a search underway for a possible second victim.
Two days later taxi driver Christopher Halliwell, 47, was charged with her murder.
Following Halliwell's trial in October 2012, a statement from Kevin was read out in court alongside Sian's families.
He said his heart had been "ripped out" and his life "destroyed" over Sian's killing.
The statement read: "Words cannot describe the pain and anguish I felt during these six days she was missing.
"My heart was ripped out, my life has been destroyed. Sian was a beautiful, happy-go-lucky person who could cheer up the most miserable of people.
"I will spend the rest of my life being grateful for the time we had together."
Halliwell was later sentenced to to life imprisonment to serve a minimum of 25 years for Sian's murder.
The events leading up to to Halliwell's jailing will be told in new ITV drama A Confession.
The series focuses on Detective Superintendent Steve Fulcher, played by The Office and Love Actually star Martin Freeman, deliberately breached police procedure and protocol to catch a killer, a decision that ultimately cost him his career and reputation.
*The Confession starts on ITV on Monday, September 2 at 9pm and has six episodes.
