Eoin Macken plays Dr. TC Callahan on the NBC medical drama "The Night Shift."

An Army doctor who has recently returned from Afghanistan and uses unorthodox methods to save lives, Callahan's brash style does not always sit well with the bosses, but he is a brilliant surgeon and a fearless advocate for his patients.

Macken recently wrapped shooting for a starring role on National Geographic Channel's upcoming event series "Killing Jesus," based on the book by Bill O'Reilly. He has also published his first novel, "Kingdom of Scars," a coming-of-age tale about a young boy growing up in Ireland.

Perhaps best known for his work on the BBC One series "Merlin," Macken starred as the swashbuckling hero Gwaine. Also for television, he starred on the Irish series "Raw" and "Fair City" as well as Masterpiece Theater's telefilm "Small Island." In addition, he enjoyed a recurring role on the Showtime series "The Tudors."

On the big screen, Macken's acting credits include "Centurion," with Michael Fassbender; Dominic West and Lee Cronin's "Through the Night;" as well as Andrew Hull's "Siren" and Mike Figgis' "Suspension of Disbelief."

A prolific filmmaker, Macken recently completed production of the feature "Leopard," on which he served as writer and director in addition to starring opposite Jack Reynor and Tom Hopper.

Macken wrote and edited his debut feature, "Christian Blake," which played at the Mid Ulster Film Festival and the 2008 Galway Film Fleadh and was released in May 2009. In 2008, Macken directed, wrote, edited and acted in his second film, "Dreaming for You," which was selected for the Los Angeles Short Film Festival and for the 2009 Galway Film Fleadh.

In 2009, Macken directed an hour-long documentary on the Irish fashion industry, "The Fashion of Modeling," which screened on RTÉ 2.