Tobias "Toby" Alexander Mills played by Henry Luxemburg made his first on-screen appearance on the 14 November 2001 and final appearance in 2003 when his character was killed off.
Toby first appears as the friend of Dan Hunter (Andrew McNair). The pair are arrested when they have a fight outside The Dog in the Pond with Adam Morgan (David Brown) and Jamie Nash (Stefan Booth). Toby moves to Hollyoaks village to help the Hunter family search for, when she went missing in . He begins working at The Dog with and begins living there. Toby is shocked when Ellie returns to Hollyoaks. Ellie warns Toby that when they had sex she may have given him gonorrhoea. Ellie tells her brother Dan and her father Les, who attack Toby. Toby keeps his distance from Ellie. He begins dating Mandy Richardson (Sarah Jayne Dunn), but the relationship ends when Toby claims that Mandy is too possessive. Toby leaves college and begins to work part-time at The Loft. However, Ellie is the manager at The Loft, which resulted in some tension between her and Toby. Dan advised Toby to not let her get to him, but with Ellie flirting with The Loft's boss, Toby couldn't help feeling jealous.
Toby soon discovered that Ellie's parents had thrown her out and he offered her a place to stay at The Dog. The pair began dating again, but Toby still disliked Ellie working for Scott. Soon Scott sacked her and Toby also quit his job at the Loft. Toby's mum Linda arrived, and she caused a stir in his relationship with Ellie. Ellie put Toby under pressure to choose between her or his mother. Toby made a difficult decision, and decided it was Ellie he wanted to be with and he told his mother that he'd had enough of her interfering. Toby was then worried when Ellie decided to go on a Reality TV program called the Fish Tank. Toby made her promise not to flirt with any men there. During Ellie's experience of The Fish Tank, rumours started to spread around the village that Ellie had slept with someone. Toby became angry by Ellie's actions and was frustrated that Ellie had not kept her promise. Toby demanded Chloe Bruce (Mikyla Dodd) allow Ellie to get out of the Fish Tank, otherwise his relationship was over with her. Ellie was allowed out for an hour, and Toby told her that he was getting impatient and angry by Ellie's lies. Ellie got upset about how little Toby thought of her, and told him that she slept with everyone.
Toby then murdered a blonde named Roxy Maguire at the River Dee. Toby was unwilling to take any responsibility for his actions. After the murder he went home and looked into a mirror and, seemingly, argued with himself, blaming someone else for his actions and telling himself that he is good. Over the next few days Toby felt guilty and especially when Ellie returned and convinced him to give their relationship one last try. A week later, Dan told Toby that he had slept with Roxy, and the police had found her body. The blame of Roxy's death went to Toby's best friend Dan after he slept with her, hours before she was murdered. Toby's best friend and Ellie's brother Dan had been arrested, but with the help of Toby's guilt, Toby provided Dan with a good solicitor as Dan had been soon released. There was not much evidence against Dan and he was released. When Toby's mother returns she tries to convince him that Ellie is cheating on him. In anger, he struck again this time on teenager Steph Dean (Carley Stenson) leaving her there for dead but the crime was witnessed and he was followed by his mother Linda. After a confrontation with his mother, Toby lashed out pushing her down the stairs. This had left Toby astonished of what he'd done, and when Ellie arrived the pair managed to make the incident look more like an accident. When the police arrived they told Toby that Linda was dead and further bad news for Toby was that Steph was alive but suffering with memory loss. Toby visited her in hospital and considered disconnecting her breathing tube, but managed to talk himself out of it. Toby was left scared of the truth being discovered and feeling guilty after Steph had developed epilepsy post-attack, a condition which she would battle for the rest of her life. He then killed around 11 more blonde girls between July 2002 and October 2003. In order for Toby to stop killing these girls, he needed Ellie to be more committed to him and decided to get married to her. Ellie was delighted as the pair got married in a low profile wedding without inviting Ellie's parents. Steph continues to make progress and begins regaining her memory. Toby confesses to Ellie, telling her that he has no control over himself during the killings and can barely remember what happened, leaving her frightened and afraid of his next move. Toby was also scared that Ellie would tell the police or her family and stopped her from leaving his flat.
In the late-night special Hollyoaks: Leap of Faith, Ellie could no longer cope with Toby and ran off to Liverpool, with Toby close in her wake. Ellie confronted him and Toby promised that he would hand himself in, but he just wanted to enjoy his last few hours with her. After the hours went by, Toby caught Ellie trying to get in contact with her brother which made Toby furious. Toby decided to bet with Ellie whether their love could survive anything, and suggested they each jump onto the opposite roof building. Ellie, however, was concerned as Toby continued to get increasingly aggressive. Dan arrived in time to witness Toby harming Ellie. In order to save his sister's life, Dan pushed Toby off the building. Toby bumped into Ellie and knocked her off too, and she fell when Dan lost his grip on her. This was witnessed by several people, including and Dan's sister Lisa, who had come with Dan to rescue Ellie.
- Unknown woman, 2nd July 2002 - Murdered by Toby near The Loft, where her body was discovered.
- Unknown woman, 27th December 2002 - Murdered by Toby near The Loft, where her body was discovered.
- Unknown woman, 20th January 2003 - Murdered by Toby near The Loft, where her body was discovered.
- Unknown woman, 25th February 2003 - Murdered by Toby in the woods, where her body was discovered.
- Roxy Maguire, 21st April 2003 - Beaten to death with a spanner.
- Linda Mills, 10th June 2003 - Accidentally pushed down stairs by Toby after Linda witnessed Toby's attack on Steph Dean.
- Michelle Reid, 6th July 2003 - Murdered by Toby before being dumped in the lake. Her body would not be found until May 2005.
- Unknown woman, 27th October 2003 - Murdered by Toby.
Toby also murdered 6 other unknown women in 2003, most likely by being beaten with a spanner.
- Izzy Cornwell, 31st December 2002 - On the night of Boy George's concert in the village, Izzy was attacked by an initially unknown man in a hood (Toby).
- Unknown woman, 31st December 2002 - An unknown woman was attacked by the man in the hood shortly after Izzy.
- Steph Dean, 6th June 2003 - Beaten with a spanner by Toby, but survived and was rushed to hospital.
- Steph Dean, June 2003 - Toby considered taking out Steph's breathing tubes but changed his mind.
- Steph Dean, 25th August 2003 - Attempted to strangle her with a tea towel but failed.
- Ellie Mills, 31st October 2003 - Attempted to kill Ellie after discovering she had been taking morning after pills but failed.
- Ellie Mills, 5th November 2003 - Attempted to throw Ellie off the roof of an apartment block, but Toby was pushed off by Dan Hunter who was rescuing Ellie.
- Toby is Hollyoaks's most prolific serial killer with a total of 13 victims, Ahead of Cameron Campbell who has 8 victims, Lindsey Roscoe who had 7 victims and Silas Blissett who had 6 victims.
- Toby was axed by producer Jo Hallows in 2003 when Toby's serial killing storyline concluded. His final episode appeared in November 2003 in which the character was accidentally killed by Dan Hunter.