When a sight zone-out occurs and Ellison is almost pasted by a garbage truck, he realizes that Sandburg is right that he needs someone to watch his back and bring him out of zone-outs.
Theorizing that Ellison's extended stay in the jungle activated his latent abilities, Sandburg wants to study Ellison for his research.
Ellison just wants the heightened senses to go away, but Sandburg convinces him that the thing to do is to get them under control.
Hearing about Ellison from sources at the hospital, Sandburg, a graduate student in Anthropology, shows up uninvited to help out.
Sandburg has warned him about the 'zone out factor', when a Sentinel gets too tuned in to one sense to the exclusion of others.
But the unlikely team of Ellison and Sandburg become close friends and the bane of criminals throughout the Pacific Northwest.
Ellison and Sandburg make an intriguing team of crime fighters, being almost complete opposites.
Sandburg is a second-generation hippie, long-haired, academic, New Agey and very talkative.
Sandburg believes that Ellison is the living embodiment of his thesis topic, a Sentinel.
So Sandburg is given permission to join Ellison's investigations as an observer.