Teen franchise hopeful “The Mortal Instruments: City of Bones” has added another young UK actor to its cast. “Misfits” star Robert Sheehan has been chosen for the role of Simon Lewis and joins a cast that already includes Lily Collins, Jamie Campbell-Bower and Jemima West. The novels’ author Cassandra Clare broke the news on her official Tumblr earlier today.

Collins stars as Clary Fray, a seemingly ordinary human girl who discovers that she can see supernatural beings that no one else can and gets drawn into the world of the Shadowhunters, humans who hunt and kill demons. Campbell-Bower is male lead and Clary’s love interest Jace Wayland, while West plays fellow Shadowhunter Isabelle. Sheehan’s Simon is Clary’s best friend who harbors a secret crush on her and plays in a band. He, too, gets drawn into the secret underground world of the Shadowhunters in New York City. Harald Zwart will direct the film in Toronto this summer, aiming for an August 23, 2013 release.

Irish actor Sheehan has a cult following thanks to his role as Nathan Young on UK teen series “Misfits”, but he has left the show, presumably in order to pursue a rising film career, which kicked off when he co-starred opposite Ben Barnes in “Killing Bono.” This will certainly prove to have been a wise choice if “City of Bones” is successful enough to spawn sequels – Clare has written five books in the main series, without counting prequels and spin-offs.