Adnan is an innocent pawn. Or at least the Adnan people KNEW was. The OLD Adnan. The one in THIS universe. In an alternate universe, he was an evil scientist with the most brilliant mind on the planet.
Alternate universe Adnan built a device. He called it the TDM, or "trans dimension machine", It was a tiny device that would fit into ones pocket. It looked very similar to a black and green one hitter with several glowing buttons on the side and a retro LED display. It was a remarkable and stylish little device capable of travel to any one of the infinite universes that exist. It would swap your body with the "you" that was in whatever alternate universe you wanted to travel to.
So when Evil-scientist-Adnan from universe SXalpha8822 traveled to this planet to check out our hopefully-advanced-technology (which didn't prove to be useful for his plans) he was stranded because his device had used its atomic charge for the month.
So Evil-Scientist-Adnan is bored, stranded on earth for a month, and decides to get high with Jay because he really likes to get high and starts fidgeting with his "trans dimension machine" and passes out. Jay sees the device and, being high also, thinks it actually is a one hitter. And he smokes weed out of it. And it actually works as a one hitter. But then he starts to feel... funny.... and before you know it he's jumping between alternate dimensions at random points in time because now he has Trans Dimensional fluid absorbed into his veins and it alters his DNA so he's continually swapping bodies with different versions of himself in different universes. But in all these Universes there's one thing that's common, Adnan thinks that Hae has the "trans dimensional device" and strangles her to death. Then when he realizes what the monster he has become he can't live with himself so he erases his own memory.
So now Jay keeps getting swapped out with different Jays from different universes, all telling their stories which are all slightly different depending on the details of their alternate universes.
And THAT was one episode of Fringe I'll never forget.