Marc and his party have finished their zeppelin and taken it out to try to discover other Safe Zones. Their intent is to set up trade routes between all the different Safe Zones in order to give them a better chance to survive.
The second Safe Zone they discover with the zeppelin is nearly as large as Any Port. It even has its own ring of outlier Safe Zones, or a partial ring at least. It appears that several of the smaller Safe Zones have been taken and converted into dungeons. With the safety of the larger Safe Zone apparently at stake, they bring the zeppelin down to help the larger Safe Zone however they can.
On return to Any Port, Marc accelerates his own expansion, his father having finally seen the wisdom of all the additional Safe Zones Marc wants in order to capture more land.
With setting up more of their own outlier Safe Zones, meeting new and interesting creatures, some of whom would like to kill and eat the party, making contact with new Safe Zones, and working with the satellite they recovered, Marc keeps himself busy in the aftermath of the System's arrival.