T-bird suddenly dead as a doornail on 2002 Ford Thunderbird

Went out this morning for an errand and the key-clicker wouldn't unlock the doors. When I manually unlocked and tried to crank the car, it was dead as a doornail. I don't know where to start as there were no prior symptoms. Recently (and still) there was very wet floorboard/carpet only on the driver's side.
Flummoxed! And I'm not even sure how to find the battery (duh!). Help?

Asked by for the 2002 Ford Thunderbird
Start with a new battery, I think AAA will come out and install a battery at your location.