They're planning on detonating a nuclear bomb in some small town outside Calgary.
I shouldn't say they, I mean we, I'm in on it somehow. There's the guy assembling the bricks around the reactor core, and there's a bunch of co-workers sheltered in a cave somewhere, trying to stay out of the line of sight of the blast ("and so the roof of the cave will glow in the dark when this is done?" J is asking....) and there's the helicopter, it has the remote control, it's going to fly close to the bomb - well, a couple of KM away, then detonate it and duck to safety behind a hill...
The timing of this is important, you don't want to be in the air when the blast hits...
I'm trying to understand the reasoning behind this bomb, but there's no reason, we're just a group of disparate strangers out for a good time, "It has to be done...." they tell me, and I'm to understand the damage will be minimal...