If the screw is recessed and spinning in the plastic, a very long thin set of needle nose can sometimes grab hold and pull it out. They also make a screwdriver that can hold the head of the screw on the end of the driver. If there is room for this tool you shoud be able to use needle nose though. Lastly, you may be able to apply pressure (pull the pieces apart) while turning the screw and get it out. But if the screw head is stripped then Jerry and Greg are spot on.
Good luck
Terry