The Warp
The Warp, called the Bajoran Wormhole by the Federation, the Celestial Temple by the Bajorans, and a number of other things by diverse other species throughout the galaxy, was an Einstein-Rosen bridge connecting the Alpha Quadrant to the distant Gamma Quadrant via a wormhole effect in space. Now, it is an Einstein-Rosen bridge connecting the Alpha and Gamma Quadrants, and... something else.
Ships can still travel back and forth through the wormhole just as they did before, but now, every time they cross it - or even come close - they run the risk of picking up unexpected guests along the way. The Bajorans believe that it is the doing of the Prophets - an advanced race of aliens who live within the wormhole. The Federation, so far, has been calling it an unexplained time-space anomaly. Either could be right, or both could be wrong; there is, as yet no way to know for sure.
What everyone can agree on, however, is that it is the wormhole that is bringing the Envoys here, and it is the wormhole that is their only way back... wherever they may come from.
Ships can still travel back and forth through the wormhole just as they did before, but now, every time they cross it - or even come close - they run the risk of picking up unexpected guests along the way. The Bajorans believe that it is the doing of the Prophets - an advanced race of aliens who live within the wormhole. The Federation, so far, has been calling it an unexplained time-space anomaly. Either could be right, or both could be wrong; there is, as yet no way to know for sure.
What everyone can agree on, however, is that it is the wormhole that is bringing the Envoys here, and it is the wormhole that is their only way back... wherever they may come from.