After Z Part 5

When the dead rose, Ryan Maxwell planned on waiting the apocalypse out in the massive Bunker he built after winning the lottery.
In the eight months since Z-Day the Maxwell family and their friends have not only NOT stayed hidden away, they have searched the country for loved ones and taken hundreds into their safe Haven.
The discovery of electromagnetic "ghosts" directing some of the undead changed the apocalypse landscape beyond anyone's imagination. But the further discovery of science that can possibly eliminate that threat may lead them down a more dangerous path.
Now, with the possibility of helping to end the zombie threat completely, they must venture farther than ever before, and in the heart of winter. Most zombies freeze in the winter, but will the cold turn out to be an ally, or just another threat to survival?
The greatest hope for the future lies buried in several heavily fortified complexes which Ryan and company must find a way to break into.
Will the most destructive technology from mankind's past be the key to ensuring it can live-on in a world…After Z?