Rupert Giles studied at Oxford University, but dropped out before earning a history degree to become a voyeur, or "watcher," as his father and grandmother Edna had been before him. Rather than taking his wayward son to task for wasting what could have been a superb education at one of the world's leading universities, Giles' father approved of his decision, affirming it as a fulfillment of his "destiny."
Before dropping out of school, Giles had been a member of Mea Culpa, a group of witches and warlocks who, instead of studying, conjured demons from the pit of hell who would help them to cheat on their academic examinations. His fellow students Ethan Rayne, Philip Henry, Diedre Page, Thomas Sutcliff, and Randall were also members of the group. Between academic terms, they succeeded in summoning Eyghon, a nasty little devil, who, for want of something better to do, slew Randall.
Giles, or "Ripper," as he was known by his fellow practitioners of the black arts, went on to found the rock and roll group Pink Floyd. Between spells, he passed the time of day stealing cars. After Randall's death, Giles decided to leave the coven and assume his "duties" as the latest in a long line of voyeurs, becoming Watcher 1008.
When he learned of the tight-fitting blouses, brief shorts, and mini-skirts that American high school girls typically wore to school, often without bras or panties, Giles left his position as the curator of the British Museum to become the librarian at California's Sunnydale High School. In the United States, Giles developed a mental disorder and, as a result, had difficulty distinguishing fantasy from reality. He believed that one of the students at Sunnydale High, Buffy Summers, was a "vampire slayer"; that another, Willow Rosenberg was a witch; and that the library over which he had charge was located over Hell.
A victim of Tourette's Syndrome, he also was given to unintelligible outbursts. To divert attention from his voyeurism, he dressed in three-piece tweed suits, maintained a ramrod-straight posture, and pretended to be confused by the shenanigans of Buffy and her friends, often mumbling incoherently. He also read occult books on arcane subjects, seeking, he maintained, "things unattempted yet in prose or rhyme." He fancied himself a detective who ferreted out thieving demons and purse-snatching vampires, earning the additional nickname "Clueless Sleuth."
Giles' mental disorder progressed during his tenure as Sunnydale High School's library, and his voyeurism made him paranoid. Eventually, when he was caught lingering near the girls' locker room, he detonated explosives he'd hidden in the library, destroying the entire school and leaving himself unemployed.
A victim of age discrimination (and insane), Giles found it difficult to acquire a new position. However, he happily accepted unemployment benefits and managed to eke out a living without having to tap his sizeable retirement fund for some time. Eventually, however, he purchased The Magic Box, selling dead rats, chicken feet, eyes of newt, and other exotic merchandise to weirdoes, punks, Goths, and the undead.
After Willow's girlfriend Tara Mustplay was murdered, Willow went mad, killing Mustplay's killer, after which Giles invited her to his family castle for tea and "rehabilitation." Months later, he returned to Sunnydale with a harem that, for reasons having to do with his mental illness, he called Potentials, meaning potential exhibitionists. He later returned to Europe, never to be heard from or seen again.
As a voyeur, Giles ogled many beautiful women, including Buffy and her friends and the following older women: Jenny Calendar, Drusilla, Joyce Summers, Olivia, Anya Jenkins, and Willow Rosenberg. He declined Xander Harris' offer to provide him with "comic relief" between girlfriends and insisted that nothing had ever happened "of an untoward sort" during his days as a member of the almost-all-male Mea Culpa coven.