|Character Profile||List of appearances|
Riley Costello was the son of Heidi and Carl Costello, as well as the brother of Seth and Jason Costello, and the half-brother of Jem Costello. He is also the father of Bobby Costello, whom was born to Riley and Mercedes McQueen, as well as Phoenix Costello, the son of Mitzeee Minniver, whom she gave birth to after Riley's death.
Riley first appears with his family when Carl buys The Dog in the Pond. Riley attracts the attention of Michaela McQueen. Zak Ramsey is jealous, so challenges Riley to penalty shootouts, unaware he is a footballer. During a fashion show for Heidi, Riley strips for the cat walk, where Theresa McQueen is attracted to him. Carl continues to push Riley into training for football. Riley and Seth are invited to a cage fighting party by sister Jem's ex-boyfriend Liam McAllister, who plans to get revenge on Carl for ruining his football career with older brother Nathan McAllister. Riley sleeps with Sami, Nathan's girlfriend, and is drugged. After Nathan and Liam lock Riley and Seth in a cage, they tie Carl up with a noose around his neck. Nathan and Liam make Riley and Seth cage fight each other, after convincing Seth that Carl is ashamed of him. The Costello's soon escape, with help from Sami, and are chased by Nathan and Liam, who have a gun. Carl manages to get the gun, and flees with Riley and Seth. Nathan follows again, and in a rooftop confrontation, he ends up falling from the roof to his death.
Riley bonds with Mercedes Fisher following her husband's death however, Carl is unhappy at their blossoming relationship. Mercedes tries to finish with him however he proposes to her she rejects but they continue with their relationship. However, Mercedes is having an affair with Carl and is nearly caught on several occasions. Soon, Riley realises that he loves her and asks her to marry him, to which Mercedes says yes, to Carl's disgust, Mercedes later discovers she is pregnant, and is unsure of who the baby's father is.
In March, he hears Lynsey Nolan being attacked in her and Cheryl Brady's flat and manages to chase off the attacker before he can harm her. However when her asks Lynsey to stay at his house with his family, Lynsey realises it was Silas Blissett who tried to attack her and escapes. In a pub confrontation, Lynsey accuses Silas of attacking her and Riley throws her out and continues to deny he attacked her, however in a meeting with Lynsey and Texas Longford Riley realises there is more to his granddad. He confronts him in the park and questions him about the attack to which Silas has a heart attack and is rushed to hospital.
In October 2011, Riley and Mercedes wedding day arrives but Mercedes is unable to deal with the guilt and reveals she has been having an affair with his father Carl. Riley then walks out of the wedding and drives off leaving Mercedes crying, a few days later Riley has a one night stand with student Ash Kane and regrets this and ignores her afterwards. Riley later attempts to call Mercedes but it goes through to voicemail he leaves a message but Mercedes is unable to reply as she is being held in a basement by Silas.
On Halloween 2011, Heidi is murdered by Silas, who mistook her for Lynsey, while walking to Cheryl's party. She is found by a passer-by, who phones an ambulance, but she is dead. Jason is informed and comes home and breaks the news to Riley and Seth. It is eventually revealed, however, that Silas is the unknown serial killer who killed Heidi and also murdered India Longford, Rebecca Massey, and Rae Wilson. Riley confronts Silas and demands to know the truth and Silas admits that he was responsible for the other murders, but swears that Heidi's death was an accident. Lynsey phones the police, who then arrest Silas and charge him with the killings. Riley and Carl find Mercedes in the basement, just minutes away from giving birth. She gives birth to a boy, whom she names Bobby Costello. However, Mercedes does not take to motherhood very well, struggling to cope. She asks Riley to take Bobby on holiday for a while, so he and Seth leave the village for a brief-break.
Riley is later seen on the TV by Mercedes, doing a shout out for Bobby. Riley returns, after Jacqui pleads with him to bring Bobby back to see Mercedes, telling him she has not been doing well in his absence. Riley asks Mercedes to sign legal papers giving him full custody of Bobby. Riley sees Darren Osborne giving away photos of the vault in which Silas held Mercedes captive. He attacks Darren, punching him and pinning him onto a table, declaring that he is selling the pub which he had given to him before he left. The next day, a guilt-stricken Darren visits Riley and pleads with him not to sell the pub and Darren later confesses to Riley that his girlfriend Nancy Hayton is pregnant with his child. Riley later forgives Darren and decides not to sell the pub after being persuaded against the idea by Lynsey Nolan. Riley helps Ste Hay and Doug Carter with their business, and in doing so, Lynsey helps them too and later she asks Riley to walk her home. When they reach Lynsey's house, Riley goes in for a coffee and the pair kiss and end up sleeping together.
Riley is distraught when Lynsey is later murdered and begins a relationship with Mercedes again, helping her after she was apparently stabbed by Mitzeee Minniver and kidnapped by Lynsey's killer, Doctor Browning. They are engaged to be married but, shortly before the wedding, Riley sleeps with Mitzeee, who is on the run from prison. Shortly after, Bobby is abducted with Mitzeee as the prime suspect. Riley ends up in a stand-off on a tower block roof with Mercedes after he later finds out that she was behind Bobby's apparent kidnap. Although Mercedes threatens to kill herself and Bobby, Riley manages to convince her to come down. When they return home, he is shocked to discover Mercedes did in fact stab herself and he watches as she is arrested. Riley leaves the house to find Mitzeee but, when he finds her, he is accidentally shot by Simon Walker during a struggle with Brendan Brady. Riley is taken to hospital but later dies, with Mitzeee by his side.
In December 2012, Mercedes is put on trial, with Doctor Browning also fabricating stories to get Mercedes released. Doctor Browning brings up the suggestion that Riley could actually be Lynsey's killer, and this is accepted by the court, resulting in both Doctor Browning and Mercedes being released, and Riley posthumously charged with Lynsey's murder. The murder charge is later cleared when Doctor Browning confesses to the murder.
- Riley Costello is the third character in the Hollyoaks universe to be played by Rob Norbury; first playing the role of Nathan Haywood from January to June 2005, then Lennox in Hollyoaks: In The City from August to November 2006.
- Norbury's decision to quit the role was announced in September 2012, with the character's final scenes airing in October 2012.