STALKER CS Need Help!

Ok I got this game and I am in the first mission at the outpost or whatever. Your supposed to go help some dude in a tower. I cant get to the tower without going through the water, I've been all around the map. So I go through the water and soon as I get to the tower I start dying from radiation I guess? Anyways, I climbed the tower and theres a guy up there just sitting there and I cant talk to him, I went into the little shack, I dont get it. What am I supposed to do there? Why do I slowly die everytime?
I've never been stumped on the first mission of a game, can someone please help me here?
Thanks

you are meant to wait for the emission, and then black out I think, I never made it to safety and then re-spawned back at the camp, until you leave for the cordon you are effectively in a training zone.

Ok, I figured it out. I guess I had to get my detector out and find the artifact before anything would happen.