Eddie Santini (Michael Higgs) first joined the relief in February 1998, in the episode Storyboards.

After he had been in the Met for seven years, he left Spicer Street Police Station, where he was working as a Trainee Investigator with CID, to join Sunhill. There was a lot of gossip about his reasons for moving. The main one was that his DI just didn't trust him. When Dave Quinnan (Andrew Paul) confronted him about it, Eddie told his colleagues that it was because he found out that the CID squad had been selling on drugs seized in raids through their informants. According to Eddie, he had asked his DI about it and soon later was turned down for CID.

Eddie was popular among most of his colleagues - good-looking, charismatic, fun with a sense of humour and rather mischievous. On the other hand, his laid-back attitude could also rub others up the wrong way.

After Rosie Fox's arrival to Sunhill, they began to appear to be a perfect couple... until Eddie sexually assaulted and tried to rape Rosie (Caroline Catz) in the WPCs' locker room after a post-op party. At first Rosie forgave him, but when Eddie found out that she had discuss the incident with a Federation Representative he began to make her life hell. When Rosie made an official complaint, he managed to convince all of their colleagues that Rosie was the one who was lying because he ended their affair. Eventually Dave Quinnan found out why Eddie had actually transferred to Sunhill in the first place: he had been accused of sexual harassment by a WDC, Jan Lockett. WDC Lockett had been forced to drop the complaint, after over a year of intimidation, and left the Met; so none of it was on his record.

The rest of the relief found out about it after Eddie failed to keep his end of a deal made with Dave and Rosie: he'd back off if they kept it a secret. Dave and Eddie had a brawl in the pub and Dave told their colleagues the truth, leaving Eddie with few friends at Sunhill.

Over the next few months, Eddie did sometimes begin to redeem himself. He earned some respect from a handful of his colleagues when he swam in the River Thames to secure a car that was about to fall over the edge of the bank. Some thought that it didn't wipe the slate clean: in the words of Polly Page (Lisa Geoghan), "He'll have to do more than get a bit wet to make up for what he did to Rosie." They found that he couldn't be trusted, particularly after he disposed of some cocaine for a dead man, and another time "accidentally" dropped a clue in front of two pimps, where to find the knifeman who attacked their tom.

At Christmas, though, he did show a real soft side when he arranged for Emmanuel Petit to visit a young Arsenal fan who had been injured in a hit and run accident.

After a while Eddie became more ambitious and wanted to transfer into the Area Drugs Squad. He used his girlfriend, Jessica Orten (Tanya Myers), to help him catch a drug importer, Tim Sherman, whilst also having an affair with his colleague PC Vicky Hagen (Samantha Robson). When Rosie returned to Sunhill, he proved how manipulative he could be. He used her own relationship with DCI Pallister (Jason O'Mara) against her, by telling him that Rosie still hadn't got over him. Eddie used Vicky to cover for him whenever he needed. He still managed to lose control when Sherman's men began blackmailing him and after an argument with Jessica he hit her, causing her to fall down the stairs, killing her. Eventually Rosie proved to her colleagues that Eddie was involved in Jessica's death, and arrested him for murder.

Eddie spent over nine months on remand in Longmarsh Prison, almost all the inmates and prison officers made his life a nightmare. The only friends he had were Vicky, who visited him once,

For his defense in court, he tried to persuade the jury that Dave Quinnan, Liz Rawton (Libby Davidson) and Rosie had framed him. Just before the trial though, he heard about Rosie's death, and again he showed his softer side as he grieved for her and used his contacts to find out who murdered her: Tim Sherman, because she and Eddie were the main witnesses in his trial for conspiracy to murder them. Eventually Eddie was found not guilty and released.

His freedom was short-lived. He went straight to his flat to find Paul Timpney there with a gun, following Tim Sherman's orders to murder him. Eddie didn't care about it though, as Rosie was dead.