Barrowman's character, according to EW, is a "well-dressed man [who is] as mysterious as he is wealthy … he is an acquaintance of the Queen family and a prominent figure in Starling City."
The cast of the new series is led by Stephen Amell as Oliver Queen, Colin Donnell as Tommy, Katie Cassidy as Laurel Lance, David Ramsey as John Diggle, Willa Holland as Thea Queen, with Susanna Thompson as Moira Queen and Paul Blackthorne as Detective Quentin Lance.
The series, CW states, is described as such: "After a violent shipwreck, billionaire playboy Oliver Queen was missing and presumed dead for five years before being discovered alive on a remote island in the Pacific. When he returns home to Starling City, his devoted mother Moira, much-beloved sister Thea, and best friend Tommy welcome him home, but they sense Oliver has been changed by his ordeal on the island. While Oliver hides the truth about the man he's become, he desperately wants to make amends for the actions he took as the boy he was. Most particularly, he seeks reconciliation with his former girlfriend, Laurel Lance. As Oliver reconnects with those closest to him, he secretly creates the persona of Arrow - a vigilante – to right the wrongs of his family, fight the ills of society, and restore Starling City to its former glory. By day, Oliver plays the role of a wealthy, carefree and careless philanderer he used to be - flanked by his devoted chauffeur/bodyguard, John Diggle - while carefully concealing the secret identity he turns to under cover of darkness. However, Laurel's father, Detective Quentin Lance, is determined to arrest the vigilante operating in his city. Meanwhile, Oliver's own mother, Moira, knows much more about the deadly shipwreck than she has let on – and is more ruthless than he could ever imagine."
"Arrow" makes its TV debut Oct. 10 at 8 PM ET.
John Barrowman is best known for creating the role of Captain Jack Harkness in the first series of Russell T. Davies' revamped "Doctor Who" for BBC TV, from which his own spin-off series, "Torchwood," was created. He has also appeared in series 3 and 4 of "Doctor Who." The singing actor has also been seen as a judge on BBC1's reality TV casting shows "How Do You Solve a Problem Like Maria?," "Any Dream Will Do" and "I'd Do Anything" and was a celebrity skater on the ITV show "Dancing on Ice." Prior to La Cage aux Folles, he was last seen on the West End musical theatre stage doing a stint in Chicago as Billy Flynn in 2004, and prior to that was seen at the National as Billy Crocker in Anything Goes (a role he had previously taken over in the previous West End revival at the Prince Edward Theatre, opposite Elaine Paige, in 1989). He also appeared as Dumaine in Shakespeare's Love's Labour's Lost during his National Theatre season, and subsequently made his West End straight play acting debut in A Few Good Men at the Theatre Royal, Haymarket in 2005. Among his other numerous West End credits are Matador, Miss Saigon, Beauty and the Beast, The Fix (Olivier-nominated for Best Actor in a Musical), Hair and Sunset Boulevard. On Broadway, he has appeared in Sunset Boulevard and Putting it Together.