Locked Out!
Thanks for the responses. The Battery was, indeed, dead. However, at the time all doors were locked and the key would not actuate the door locks. I am not sure if the temp, low 30's, had something to do with that or if the battery just needed a little time to "juice up".
At any rate, after contemplating what to do while all my buddies were in a deer stand freezing, I went back a little later and the drivers side door was unlocked. How strange, I thought. Well by that time our local Ford dealer service department was awake and hard at work. They also suggested that I check out the battery.
I replaced the battery, which seems to have resolved the immediate issue. I still don't know what caused the battery to go down, nor do I understand why the key would not actuate the locks.
Again, thanks for the responses. Have a great Ford Explorer day!