Two hundred years ago, the Union of Worlds investigated our corner of the galaxy. The violence they witnessed on the face of the planet Earth repulsed them, and prompted a barricade between us and the rest of the intelligent universe. This solution could only last for so long though.
More recently, when two teenage aliens too curious for their good inadvertently made first contact with humans, the Union of Worlds had to do something. With the violent assessment of the planet's inhabitants from centuries past still holding sway, the universe's governing body wanted nothing to do with Earth. They certainly didn't want to induct such a barbarous species into the Union of Worlds. As a compromise, they put a simple trade agreement into place with our planet and washed their hands of us. Although this seems agreeable at first glance, the goods being exchanged are unregulated as Earth has no standing in the universe’s governing body.
Specifically, one good; Stim-X; leads to problems. A powerful stimulant with devastating long term side effects baned most places in the universe finds its way into the hands of the general population. Specifically, our hero Lin gets hooked before the dangers of Stim-X are known on Earth. When he tries to both get clean and bring the ugly truth of the drug to the attention of the government he inadvertently gets sucked in the the thick of the action. Now in space taking his complaints directly to the Union of Worlds, Lin questions whether he’s cut out for the gallant life-changing adventure he’d always dreamed of having.