1. The types of magazines each species creates is different (and mostly fairly stereotypical). Dwarves are big on science and geology, jewelry and other crafting. Elves tend toward the new age-y. Hobbits are where you get all your farming and food related needs. Men are more travel guides and anthropology (national geographic) types.
2. Bilbo is a reporter for a farming magazine and is working on a piece comparing different fertilizers. In his research, he’s come across some alarming stories and anomalous information about a particular fertilizer. Since he knows little about chemistry, he has to go and find someone who can tell him what’s causing the problems.
3. This leads him to the Dwarves. They have the skills to break down and analyze the fertilizer, and Bilbo provides lab space for them.
4. It turns out that the fertilizer has dragon poo in it. This makes plants grow really fast, but also has all kinds of nasty side effects on the plants in question and also is bad for people to be around. (I mean, usually you think that it’s a bad idea to be around dragon poo because that probably means a dragon is nearby, but no. It’s really just no good for you.)
5. In the ensuing examination of the Smaug Company, they discover at least one dragon being held captive. They are also using scales and claw trimmings in their various products and the dragons are in poor shape. They free them and take them in, protecting them because Smaug’s treatment of them has left them very vulnerable. But they are still really good at starting forge fires and protecting valuables like gold and babies.
6. Bilbo wins an award for his article.