Jim Ellison was a U.S. Army Ranger who spent 18 months in the Peruvian jungle after his unit was killed. During this time, he developed hyperactive senses that came online five years later, when he was a detective in Cascade PD's Major Crimes Department. When he goes to the hospital to see a doctor, he finds instead Blair Sandburg, an anthropologist from Rainier University who tells him that he's a Sentinel. In ancient tribes, Sentinels protected the village. For Jim, Cascade is his village. Blair has been studying Sentinel mythology for years, but he never found before a person with all five senses enhanced, a true Sentinel.