taillight fuse

I am working on a 98 Buick LeSabre that has a Fuse issue with the taillights. Well I started tracing the wiring, using a bulb in the fuse socket - the bulb lights up but ass soon as I unplug all the connectors to the rear taillights the light goes out, and whenever I plug any of the connectors it lights up like that power wire has ground. I unplug the bulbs and the light is out, I even tried replacing the bulbs and still no difference.