The following is a list of characters who first appear in the fourth series of the BBC school drama Waterloo Road, in order of first appearance. The fourth series consists of twenty episodes, first broadcast from 17 January to 20 May 2009. The main cast remains mostly unchanged from series 3, augmented by Rob Cleaver in the first ten episodes and returning character Kim Campbell from episode eleven. The Kelly family, consisting of mother Rose and her children Marley, Earl, Sambuca and Denzil, all first appear in episode 1. Head Girl Flick Mellor and her father Ralph, head of the board of governors and local police chief, also debut in episode 1, as does head of extended services, and sister to head teacher Rachel Mason, Melissa Ryan. Melissa's son Phillip and security guard Dave Miller first appear in episode two, and pupil Lauren Fletcher (later Lauren Andrews) makes her first appearance in episode six.
Rob was a former drug addict who was fired due to him taking performance enhancing drugs at his old work. He lied about it at Waterloo Road and said he injured himself. All is revealed when he is seen giving Bolten Simile the very same drugs which ends his time at Waterloo Road.
Sambuca Kelly made her first appearance in Waterloo Road on 7 January 2009 during the fourth series. She is the daughter of Rose Kelly. Sambuca was killed-off in the seventh series on 8 June 2011 when she died from a long-term brain tumour.
Sambuca arrives at Waterloo Road with her mother and brothers in the first episode of series 4. When her younger brother, Denzil Kelly is framed for possession of a gun on the school grounds, Sambuca and her siblings are separated and taken into temporary foster placements. Sam is fostered by her music teacher Matt Wilding, which causes a violent outburst with Sam's abusive father, Reynold Kelly. Eventually, Denzil is released from youth custody and Sam's older brother, Earl Kelly is arrested for the murder of Maxine Barlow. Sam defends local gypsy travellers when they come to Waterloo Road, including one of them named Kyle Peters, who Sam develops a crush on. Eventually, Kyle and the other travelers return to their home at the caravan park. In series 5, Sam is seen to be close best friends with Lauren Andrews and Cassie Turner, who is seen to make accusations of bullying, when really she suffers the mental illness, Schizophrenia.
In the beginning of series 6, Sam is framed by Amy Porter when she stashes drugs in Sam's coat pocket. Sam is suspended by the head teacher, Karen Fisher, but eventually Amy and Lauren both admit to setting Sam up. Sam rejects the offer to stay in Waterloo Road, as she believes that nobody will ever believe her again after Amy's stunt. Sam leaves temporarily and ends her friendship with Lauren. Sam returns several months later and she decides to get her own back on Amy after she set her up with drugs. When Harry Fisher steals his mother's phone to message several teachers, impersonating her, a voluntary bag search begins and Sam plants the phone on Amy. Harry eventually admits to his practical joke and is suspended for a week, while Sam eventually re-builds lasting friendships with Amy and Lauren. Sam isn't happy to see Finn Sharkey with her brother, Denzil. As she believes that Finn is a bad influence on her brother, Sam is determined to keep Denzil away from Finn. After Finn hosts a party, Sam comes to terms with her feelings for him and they begin a relationship, which is tested to the core when classmate, Kyle Stack gets the leading part in a school pantomime, Cinderfella. As Kyle and Finn continuously wind each other up, Sam is upset when Kyle is pulled out of the panto and Finn is given his main part, as Sam believed that the panto meant everything to Kyle, even if he didn't show no feeling towards it. When Denzil experiences near death when he pulls a dangerous stunt, Sam is horrified when Finn falls from the high bridge after rescuing Denzil from nearly being killed. Sam blames Kyle for Finn's accident, but Sam, Kyle and Finn all put their differences behind them and start afresh as friends.
In series 7, Sam and the rest of her friends discover that Kyle may be the father of his girlfriend's baby. Sam supports Kyle's decision to step up and be a father to his baby, although it is revealed that Kyle is not the biological father. Sam experiences nausea and severe migraines and after collapsing into a seizure in front of English teacher, Tom Clarkson, Sam is later diagnosed with a long-term inoperable brain tumour. Sam's mother, Rose Kelly is determined to get a second opinion in order for her daughter to get better, but it is clear that nothing can cure Sam's tumour because it was diagnosed too late. Sam discovers from her doctor that her condition is incurable and she is dying. She continues further treatment with the support of her family and friends. Sam and Finn's relationship falls into jeopardy, as Finn feels he can no longer cope with Sam's condition, but he later has second thoughts and their relationship is back on track, with Finn supporting Sam through her decision to stop her treatment. Sam goes on a day trip with Finn and Lauren in order to find the father who was never there for her when she was growing up. Sam finds out from the mother of her father that Reynold is in prison for life after assaulting someone. Sam resents her grandmother immediately when she makes cruel remarks about her and her family. Sam, Finn and Lauren all go to the beach, where Finn and Lauren go skinny dipping and Sam watches. Sam confides in Finn that she is scared of dying. After a long day, Tom takes Sam and Denzil home and Sam's condition becomes worse. After experiencing one of her migraines and vomiting, Sam lies in bed with Tom and Rose beside her. Tom hands Sam a photograph of her father, given to him by Reynold's mother. Sam screws up the picture and says to Tom that she wishes he would've been her dad and not Reynold. Tom and Rose comfort Sam, who later dies in her sleep. A memorial service is taken place at Waterloo Road for Sam just a few weeks after her death and a tree is buried in her memory by the students.
Denzil Kelly, played by Reece Douglas was a character and a pupil who made his first appearance in Series 4, Episode 1 and made his last appearance in Series 7, Episode 30 when he was killed in a lorry crash.
