well that's easy but can be a pain turn off the breaker in the panel take the plugs off one at a time till you find the plug that when taken off cuts power to the rest of them it helps to use s lamp or radio for this even better is a voltage detector like you see mike holmes using on holmes on homes in which case you take them all off and then test each wire till the tool beeps at you or you can write down the panel info and go to home depot and get a gfci breaker if you want further info I am an electrician send me an email
k.d.puffer@gmail.com