Marty, I'm sorry. But the only power source capable of generatin...
Dr. Emmett Brown: Marty, I'm sorry. But the only power source capable of generating 1.21 gigawatts of electricity is a bolt of lightning.
Marty McFly: [startled] What did you say?
Dr. Emmett Brown: A bolt of lighting. Unfortunately, you never know when or where it's ever gonna strike.
Marty McFly: We do now.
[hands Doc the "Save the Clock Tower" flyer]