Despite the way it seems, this is actually a Forgotten Realms game. Kind of. In an odd sort of way that has proven to be quite fun in the past.
Your characters will start in the Modern world, and will wind up being teleported to the world of Forgotten Realms. They will retain their D20 Modern classes, as well as all their knowledge.
This is why the D20 Modern craft skills are highly recommended. Characters will be able to create mechanical objects, and will be limited by only five simple rules.
Project Blue Phase. One of the United States government's scientific black projects. Using the best and brightest, it's eventual goal is to transport teams from our universe to a parallel universe that has been identified as very similar to our own, and then for the teams to return using equipment on that end.
In addition to scientists, the project also employs a small force of military personnel, to dissuade curious eyes from attempting to glimpse what is inside the compound. This is a good thing. Because the scientists have almost made a breakthrough.
The machine on which they have been working is almost complete, and contact has been made with a team of scientists that is slightly ahead from the parallel universe. It is almost time for a team to be assembled for a trip to the other side.