Dillon joined the team at Holby A&E as staff nurse before the beginning of series 16. We later found out that Dillon had been at medical school but had left before finishing the course, deciding that the huge pay packet and whole "my son's a doctor" routine wasn't for him. Dillon was a Samaritan, but kept this to himself until one of his callers was brought into A&E.
When the sister of homeless teenager Gemma died, Dillon did his best to help her - but Gemma wouldn't have Social Services involved, and begged Dillon to help her himself. Dillon let her stay at his place for a few days, but was embarrassed when Gemma made a pass at him. He suggested she should try to find somewhere to live. The same day Gemma, wandering among the traffic, covered in cuts and bruises, was brought into A&E. She claimed to have been knocked doen but there were no signs of such injuries. When he heard about the situation, Charlie was not happy, thinking that Dillon was taking the Samaritan thing a bit too far, and Gemma was taking him for a ride. Dillon wouldn't listen, however, and believing Gemma's story, he took her home. He soon found her a place in a hostel though. But not long after he had dropped her off, she was brought back into A&E, having cut herself. This time Charlie managed to persuade Dillon that he'd done enough and should break ties with Gemma. After Gemma discharged herself and phoned Dillon, hysterical, Dillon wanted to go and find her, btu Charlie refused to let him leave the shift. When he arrived home, he found Gemma unconscious on the floor, having taken an overdose. He rushed her to A&E but there was little anyone could do, and Gemma died. Dillon was furious with Charlie, saying they could have helped her if he'd found her earlier.
Tony Vincent started dropping hints to Dillon, suggesting Dillon was gay. Dillon eventually snapped and denied it - the fact that he hasn't had a girlfriend for months means he's fussy, not gay. He suggested that Tony fancied him, but said he was out of luck. When Anna also mentioned that she had thought he was gay, saying it was his blond hair, Dillon decided to try to do something about it. He asked Anna if she was doing anything tonight, making sure Tony heard, and got Anna to help him dye his hair. When the others weren't too impressed with the result, however, he washed out the dye.
At the beginning of series 17, Dillon was delighted to be asked out by locum SHO Heather Lincoln. They spent the night together, but the next morning Heather was annoyed when Dillon was more concerned about Lara, in court charged with manslaughter, than with her. She flirted with Simon to try to pay him back, but later forgave Dillon. After the shift, Dillon went to court in time for Lara's verdict, and was shocked to hear that the jury found her guilty. He tried to comfort Lara, reassuring her that she would not get a custodial sentence, and was shocked and upset when Lara was sentenced to three years' imprisonment. Visiting Lara before he was due to go on a date with Heather, Dillon cancelled the date after finding Lara in a bad way. Soon afterwards he discovered that Heather had slept with Simon, but when he confronted her Heather told him he didn't have exclusive rights to her. After arguing with Simon over a patient, Dillon banged his head against a locker and thumped him in the stomach, saying, 'That's for sleeping with Heather.'
Dillon had a new problem to face when during a shift at the Samaritans, he received a phone call from a distressed woman who had abandoned her baby. He eventually realised he was talking to his colleague Roxanne, but Roxy hung up as soon as he told her. After Roxy found her baby and brought her into A&E, not saying anything about why she was ill, Dillon decided to tell Charlie. But he was not happy with the way Charlie dealt with the matter.
Later in the series Dillon started seeing Roxy, but when he took some of his colleagues to the restaurant where Roxy was moonlighting as a waitress dressed as a schoolgirl, Roxy was not amused and promptly dumped him.