Young Merlin (Colin Morgan) is a teenager, discovering and then learning to master his magical gift. Magister Gaius (Richard Wilson), King Uther Pendragon’s (Anthony Head’s) learned court physician to whom he’s assigned as humble page, teaches him medicine, coaches his magical self-study, and warns him of Uther’s strong aversion to magic. Merlin becomes squire to the noble but imprudent crown Prince, Arthur (Bradley James), whose fate is linked with Merlin.