Faith (Hangul: 신의; hanja: 信義; RR: Sin-ui; also known as The Great Doctor) is a 2012 South Korean fusion fantasy-historical-medical television series broadcast by SBS from August 13, 2012 to October 30, 2012 on Mondays and Tuesdays at 21:55 for 24 episodes. It is about a modern-day plastic surgeon (Kim Hee-sun), who gets kidnapped and travels back in time to the Goryeo period, 700 years in the past. There, she meets and falls in love with a warrior, who is the leader of the royal guard (Lee Min-ho)
After King Gongmin of Goryeo marries the Yuan princess Noguk, they return to Goryeo. On the way they are attacked and the queen is fatally injured. According to the advice of his royal advisor, the king orders royal bodyguard Choi Young to pass through a mystical portal (“heaven’s gate”) and find “heaven’s doctor.” Choi Young travels to the future and brings back Yoo Eun-soo, a modern-day doctor from Seoul, who saves the queen’s life. He makes a promise that he will return her to her world, but the scheming royal advisor persuades King Gongmin to force Eun-soo to stay as she can be useful to him.
As Eun-soo accustoms herself to her new surroundings, gradually she and Choi Young fall in love with each other. But problems arise as others become fascinated with her as the ‘Heaven’s doctor’, and Eun-soo becomes a pawn in the political power plays between Gongmin, the Yuan overlords, the sociopathic nobleman Ki Chul and Prince Deok Seung, King Gongmin’s uncle. Constantly risking his life, Choi Young thwarts numerous attempts by Ki Chul and Deok Seung to kidnap and possess Eun-soo, the worst of which almost results in the death of the king and queen.
Choi Young brings Eun-soo to the portal before it closes so that she can travel back and bid farewells to her loved ones and join Choi Young permanently, Ki Chul attacked them and Choi Young suffers a life-threatening wound. Ki Chul then drags Eun-soo to the portal, and Eun-Soo enters it hoping to save him by gathering medical supplies from the future. When she passes through the portal again, she finds herself in the era a hundred years before Choi Young’s time. There, she spends a few years waiting for the portal to open again, while leaving hints for her future self. One day, “heaven’s gate” opens again and Eun-soo enters, only to find herself again back in modern-day Seoul.She re-enters the portal and travels to the time period five years after she left Choi Young, a time during which he has brilliantly won a number of military battles and reclaimed lands of Goryeo. Finally she and Choi Young reunite.