The 68 were soldiers and civilians who participated in the massacre and looting of the Janasthan area of India during the British occupation. Because of this atrocity, a dying Snake Spirit (Naga) cursed these individuals to be constantly reincarnated in each generation, having their best and worst character traits follow them from life to life. The leader of the group, Captain Jonathan Harker, was cursed with the added ability to remember every event of each of his previous lives; he therefore set out to create a society for the preservation of his and the other immortals' legacy. He named this secret society simply The 68.
To identify themselves, those indoctrinated into The 68's ways are identified with tattoos of emblems from the initial Janasthan attack -- the crest of the East India Trading Company, images from the Janasthan snake temple, et cetera. There is a very strict heirarchical order established, as well, which dictates the status of each reincarnated member into castes. The punishment for one of the lowest caste members even touching one of the highest caste, for example, is death.
The 68's main purpose is the maintenance of their own order, and thus its main task to that end is the elimination of each generation's Snake Woman - the initial Naga Spirit's tool of vengeance, a seemingly normal human woman who, when under extreme stress or exposed to one of The 68's symbols, is imbued with the powers of the Naga. Should any Snake Woman eliminate that generation's entire group of 68 reincarnated souls, the cycle would be complete, and none of the souls would be reincarnated again. She has yet to succeed, but this time, something is different; Jessica Peterson, our generation's Snake Woman, has help from the inside, and she is determined to succeed where all her previous lives have failed.