After you grab the envelope the guy on the Antennae who would not talk to you before starts yelling for you to come help him.
When you get there he tells you that he needs your help finding his son Christoph. He fills you in on what he wants you to do. He promises you a special weapon if you look for his son at the Tower.
When you talk to Ayo he tells you that the kid was last seen out by the skyscraper - but that with the low batteries it could be just the radio not having the power to reach the Tower...
As you make your way to the marker you get a radio message from Christoph that both reveals his true position - which is nowhere near where we thought it was - and that he has found some other survivors - but he needs help.
Christoph was grinding the starter on the bus which was drawing in the infected - you get him to stop, and then you have to clear out the infected to secure the Safe Zone. So you may as well start with closing that gate?
You may want to jump inside the building and restore the power first so that after you clear away the infected you automatically clear the zone...
With the zone secured you then open the bus and talk to Christoph - and you have the conversation with him that his Dad wanted. The problem is that Christoph is not interested in working for Rais.
Your deal is simple -you convince his Dad to quit Rais and Christoph will stop being a runner and work with his Dad to make weapons for Brecken.
With that deal done, it is time to head back to the Radio Tower to talk with his Dad - and you explain the way things are. He wants to save his son he needs to quit Rais - but the problem is that Alexei does not believe that the Tower is safe.
Still you are a pretty persuasive fella, and you manage to convince him! Ah, but then Rais' men attack!
After you defeat the squad from Rais you talk with him again and he is now fully committed to the plan. He tells you about a special weapon he has created but not crafted - the Zombie Classic Blueprint - an electric Machete - that may very well be nearly a perfect weapon! Mission accomplished!
Collectibles
Battle Journal #08 - Inside the Safe Zone Hotel.
Home Run Blueprint - Inside the Antenna Safe Zone