After the outbreak of the deadly Red Plague and global nuclear war, humans have largely become extinct, with the few surviving ones becoming
mutants, having been affected by radiation. The Elder (voiced by Gergo Danka), the only person with the knowledge of the past, resides in the Ark, a fortified settlement that serves as the last bastion of civilization. With severe resource shortages, the base sends out special mutants called Stalkers who scavenge resources in the surrounding wasteland known as the Zone. However, the Zone is also populated by Ghouls, human survivors driven violent and insane from the aftermath of the bombings who worship the old world civilization as the Ancients. Two Stalkers, Bormin (a humanoid boar voiced by actor
Enzo Squillino Jnr) and Dux (a humanoid duck voiced by Jared Zeus), are tasked by the Elder to head north to search for another Stalker, Hammon. Hammon is a technical genius and is the only person capable of keeping the Ark's systems running, but he and his team disappeared during an expedition, and his absence puts the entire Ark at risk. Bormin and Dux set off to find Hammon, finding clues that he journeyed north to investigate a strange craft that crashed from the sky, believing it holds the key to finding the mythical promised land of Eden. As they travel north, they find and rescue Selma and Magnus, Hammon's fellow Stalkers. They also learn of the Nova Sect, a group of fanatically religious Ghouls who seek to restore Ancient weapons technology that can be used against the Ark. The Nova Sect was able to capture Hammon, and are attempting to force him to assist in their plans. The Stalkers journey to the Nova Sect's headquarters, the Spear of Heaven. Along the way, they recruit Farrow, a Fox mutant determined to get revenge on the Nova Sect for destroying her settlement. They attack the Spear of Heaven and break into an Ancient underground bunker where they find Hammon. Hammon reveals to them that Eden does exist as a secret Ancient facility that holds information on the origins of mutants. However, the Nova Sect were able to read his mind and discover Eden's location, and are heading there to learn its secrets. Hammon directs the Stalkers to beat the Nova Sect to Eden to ensure its knowledge does not fall into the wrong hands. In order to reach Eden first, the Stalkers will have to travel through the Forbidden City, the ruins of an old Red Plague quarantine zone populated by hostile Ancient robots. Disobeying the Elder's orders, the Stalkers journey through the Forbidden City, where they find the Nova Sect and their leader, Plutonia, attempting to break into Eden. The Stalkers are able to eliminate the Nova Sect and kill Plutonia, and Eden's gates mysteriously open for them. The Stalkers enter Eden and explore the facility, discovering that the Ancients were experimenting with creating mutants before the project was shut down. They are then shocked to find out that the Elder himself was one of the scientists in charge of the experiments, and they remember how he smuggled them to safety to prevent them from being destroyed. At that moment the radio activates and they hear a voice calling for "Command Center Sweden."
Seed of Evil Plot of the expansion continues the story of the original game. When the Elder learns that the Stalkers have disobeyed him, he leaves the Ark. Some months later, the team tracks him down in the northeast where a mysterious plant growth had started to spread, also affecting the Ghouls. They confront him, but the Elder escapes to space with a rocket shuttle. After returning home, the Stalkers find the Ark under attack by intruding vines, with some inhabitants also behaving strangely. The community has put the bartender Pripp in charge while they were gone, but he is not competent enough to deal with the situation, so he asks the Stalkers for help. Together, they figure that a likely culprit is the mutant Goran who has the ability to control plants and has been banished from the Ark some time ago. Stalkers venture further northwest where Goran is thought to have a base, a second Ark not known to the Elder. They are joined by a new mutant, Big Khan (a humanoid
moose) who has been wandering the Zone alone, and has also noticed the new threat. They find Goran in a deserted town and kill him during a fight. It turns out that Goran was also absorbed by plants and had his own will replaced. In that moment, a being called Old Jyko contacts them
telepathically, and beckons them over. Old Jyko, whom they know as the oldest tree in the Zone, sends her minions after the Stalkers when they arrive. During the ensuing fight, they destroy her spore pods which kills Old Jyko. She collapses through a hole in the ground, revealing hallways with familiar logos of Mimir corporation which they saw in the original Eden. It is another secret base. The only functional computer reveals that their Elder was a project leader here too. Scientists wanted to design a tree for purifying the air using the same method of creating mutants in a last-ditch effort to save the humanity, but were forced to abandon the base when the war broke out. The tree survived, became self-aware, and decided to "purify" all the creatures in the Zone by transforming them to mindless drones under her control with spores. When they return, the Stalkers are treated to a heroes' welcome, and Bormin is elected new leader of the Ark. ==Development==