James Ellison grew up in family that didn't encourage emotionalism and stressed competition. After years of constant struggle with his younger brother Steven for the approval of their father, Jim joined the military. Jim's miltary experiences remain largely unexplored, but he has revealed to his partner that he spent time in Covert Ops. Jim's last mission ended when they crashed in the Peruvian jungle and his entire team was killed. The sole survivor, Jim was stranded in the jungle for 18 months before being rescued.
It was his experience in Peru that brought Jim's heightened senses to the surface. Under the stress of needing to be constantly alert to stay alive his abilities, previously hidden, erupted full force to help him survive. After his rescue and his return to the relaitve civilization of the United States, Jim's abilities faded back beneath the surface, leaving his experiences in Peru a vague, confusing memory.
But five years later Jim's abilities resurfaced. With no understanding of what was happening to him, and no memory of how he coped in Peru, Jim was forced to seek help. Instead of a doctor or a psychologist, he found a grad student majoring in anthropology. The student, Blair Sandburg, revealed that Jim's abilities are part of his genetic heritage as a Sentinel, a genetic 'throwback' to a precivilized breed of man. The Sentinels were the guardians of the tribe, using their enhanced senses to protect the people around them.
Reluctantly, realizing that no one else would be able to help him, Jim allowed Sandburg to train him in the use of his abilities. Blair would help Jim gain control, and in return Jim allowed Blair to study him for his thesis.
The arrangement is rocky at best, but over the course of two years the unlikely alliance has blossomed into a rewarding friendship. The two men have become so comfortable with each other that Ellsion - the living epitome of the phrase lone wolf - even allowed Blair to move into his loft after the younger man's apartment was blown up in a drug raid. Jim's "Allright. Look...one week!" seems to have stretched into a year and a half with no complaints from either party - even after the ape trashed his apartment twice! That's gotta be friendship. His protectiveness of his guide has only grown since the beginning of the series, despite the fact that Blair is in a much better position to defend himself now than he was before.
Jim is gaining more complete control of his abilities, but he still needs Blair around to guide him. Blair's techniques help Jim control sensory overload, filter out background noise and focus. Without Blair, Jim has a tendancy to zone-out, to become lost in one sense. He focuses so hard on that one sense that everything else is drowned out, leaving him in a deep trance-like state and extremely vulnerable.
In order to prevent a zone-out on the job, Jim's boss, Captain Simon Banks, has reluctantly allowed Blair to become a police observer, and Jim's unofficial partner. Between the two of them, Jim and Blair end up dealing with more than their fair share of whackos, psychopaths and revenge-crazy lunatics, leading one to wonder if Cascade's mental institutions need to beef up security. Despite this, Ellison has the best case solved record in the department, and his help from Blair makes a lot of it possible.
Blair grew up in a rather unusual family. An only child, his mother was a single parent who didn't seem to want to let go of the 60's. Her philosophies of love, peace and freedom have strongly influenced Blair's outlook on life. Strongly pacifistic and almost naively innocent it's hard to imagine that the capacity for violence exists in the long haired anthropologist. Blair is anything but weak, despite his unassuming stature. On more than one occasion he has saved Jim's life or dealt with the criminal du jour before things got out of control. Preferring to use his wits to his fists, Blair has held his own against right-wing extremists, cop-killers and serial killers.
Oddly enough, Blair's involvement in Ellison's life was the result of a quest for knowledge, not adventure. Blair's studies of the ancient civilizations led him to discover the concept of Sentinels; men and women with heightened senses of sight, touch, taste, smell and hearing. Sentinels protected the tribe, keping the people safe from natural disasters, criminals and wars. Intrigued to the point of obsession, the study of Sentinels has made up the majority of Blair's studies through his education. Years spent looking for a true, living Sentinel were realized when he met a desperate police detective named James Ellison. Ellison's Sentinel abilities had developped and the man was unable to control them.
Blair approached Ellison and cut a deal: he would train Ellison, explain how to control his abilities, and in exchange Ellison would allow Blair to use the information he gathered in his thesis. Essentially, Jim is the subject and Blair is the researcher. The relationship got off to a bad start - Ellison threw Blair against a wall - but over time, as they continued to work together, they learned to live with each other. And Blair seems to be using his knowledge of Jim to his advantage; he easily guilted the older detective into allowing Blair to move in with him after the anthropologist's apartment was blown up. He even got Ellision to agree to let the ape stay.
Blair's position as observer at the Major Crimes Unit of the Cascade PD serves a purpose; allowing Blair to make sure that Jim's abilities don't get the better of him while he's on the job. Blair's presence is necessary, without him Ellison would have long ago succumbed to sensory overload. And while Jim's boss and coworkers didn't much care for the 'neo hippie punk' at first, they seem to have come to treat him as one of their own.
Blair himself has come to see Jim as more than a thesis. "It's about friendship," he told Jim, and he's proven it time and again.
The captain of the Major Crimes Unit and Jim Ellison's boss, Banks is the only person besides Blair who knows about Ellison's Sentinel abilities. He was told out of necessity in the second episode when Ellison was making arrangements for Blair to become an observer. Banks doesn't fully understand the Sentinel abilities - he doesn't fully understand Sandburg, either - but he's willing to cooperte with Jim and allows him a lot of leeway that normally wouldn't be there. He puts up with a lot from those two, and one has to wonder how much fallout he catches from some of their wilder cases.
Banks is a recently divorced father of one - his teenage son Daryl appears early in the first season. He's a good cop, as we see in several episodes in which he is a main figure, a caring father and an old friend of Jim's. He has a tendency to yell a lot, but he's very protective of his people.