Dr. Maxis and his scientist team, Group 935, were tasked with creating an army of super soldiers and new technology for the government project christened "Der Riese" or "The Giant". In his experiments, Maxis used Element 115 to create the zombies. The zombies, however, couldn't be controlled and would always be killed when they went berserk. While this was going on, Richtofen was testing 115 on living test subjects to create his super soldiers. In his experiments, Richtofen used Takeo, Nikolai, and an unknown Mexican (Most likely Harvey Yena) . When Richtofen accidentally killed the Mexican, he replaced him with Dempsey. Dempsey had recently been captured when he led a Marine Recon team, the 4 marines in the first 2 maps, to rescue Dr. Peter McCain, an OSS spy sent to infiltrate Group 935. The testing affected each of the subjects' minds, making Dempsey extremely aggressive, quieting Takeo into only reciting Japanese proverbs, and making Nikolai functionless without vodka. It erased their memories, and Richtofen also did testing on Samantha.

The new weapons Group 935 created were also powered by 115. Maxis created the Ray Gun based on plans received from Shi No Numa. Richtofen created the Wunderwaffe DG-2 from 115 and the Monkey Bomb. Maxis promised to mass-produce the DG-2 to his superiors, but his growing infatuation with Sophia slowed his progress and infuriated Richtofen, who then plotted to overthrow him and take control of Group 935.

Maxis also created 115-powered teleporters, but they would always destroy anything sent through them. All of these experiments were done with his assistant, Dr. Richtofen. When he used his daughter Samantha's dog, Fluffy, as a teleporter test subject, he accidentally created the first hellhound. The dog was teleported, but instead of being destroyed like the past test subjects, she was zombified. When Samantha came running in and started questioning her dad about her dog, Richtofen left the room. Richtofen then followed through with his previously-planned betrayal by locking Maxis and his daughter in the room with the hellhound, which was originally believed to have killed them. Maxis and Samantha were killed and the zombies were unleashed, with Richtofen and his super soldiers escaping before being overwhelmed.

In the introduction to Kino der Toten, Richtofen reveals that he knows much more about the energy created by 115, and that he was excited to learn that it was also capable of time travel. He seems unconcerned that he and his partners have been teleported to Nazi Germany in an unknown year.

Sometime prior to Ascension, Yuri Kravcheski was transferred to work on sending monkeys into space, much to his dismay. His transfer was caused by his superior, Gersch, who he holds a grudge against. As the radio messages progress, Yuri notices the teddy bear and the Matryoshka dolls and wonders how a child could be let into the station. A child then slowly drives Yuri insane. Yuri, in his state of insanity, finishes the Gersch Device and has Gersch activate it, letting in the zombies and seemingly killing Gersch. Yuri soon realizes his mistake and is heard screaming at the end of the last recording.

After the events of Kino der Toten, the main characters somehow reach the abandoned Soviet launch pad in Ascension. When the game starts, the four are landing in the starting room on the lunar lander as the color turns to black and white (which the characters acknowledge). The characters then hear Gersch, who tells them that the mechanism must be repaired. He is referring to the Kassimir Mechanism, which must be repaired by completing different tasks. After all of the tasks are completed and the mechanism is repaired, Gersch is free and gives the players 90-second death machines.

While the events of Ascension are occurring in Russia, the events of "Five" are also unfolding in the Pentagon. While John F. Kennedy, Robert McNamara, Fidel Castro, and Richard Nixon are negotiating, zombies break into the Pentagon with only the four of them left to fight them. While fighting, they call the characters in Ascension using three red telephones spread across the Pentagon. A piece of Intel reveals that all Wunderwaffe materials were to be moved to American-controlled installations. As a mainframe is visible behind one of the windows in "Five", it is apparent that it was moved there as per this order.

Sometime in the present, George A. Romero stumbled upon Group 935's research while making a WWII film. He and the cast took a ship out to an abandoned lab in Siberia. After he and the ship's crew were zombified, only the cast, made up of Sarah Michelle Gellar, Robert Englund, Danny Trejo, and Michael Rooker, remained. This set the stage for Call of the Dead. After the Kassimir Mechanism was completed in Ascension, it overloaded the teleporter and sent the original characters to a Group 935 facility in Siberia, where they were trapped behind a locked door. The celebrities then helped them escape to Paradise. Escaping isn't Richtofen's only goal, however, as he meant to travel to the Siberan facility to obtain the Golden Rod, which the celebrities were all too happy to give to him. It is unknown what became of the celebrities after helping the group escape.

Shangri-La, however, does not live up to its namesake, as its inhabitants have all been zombified before the group's arrival. Richtofen states that this is the last step to controlling the world before he is teleported there. The temple houses a mining facility filled with Element 115, explaining the inhabitants' zombification. Prior to the group's arrival, two explorers, Brock and Gary went on an expedition to prove their theories on Argatha. After investigating the temple, the pair accidentally travel back in time, as signaled by the sudden eclipse. Gary is killed by the zombies while Brock is trapped and dies. The group travels back in time and helps the pair survive by saving them from the temple's various traps. The pair's changing fate is illustrated by the radios that materialize as the group helps them. Also materializing are crystal orbs that appear on the tops of various temple structures. The final step to freeing the pair has the group using a Pack-a-Punched 31-79 JGb215 on the gigantic 115 meteor that crashed into the top of the temple, creating the Focusing Stone, which subsequently lands on an altar with Richtofen's name written on it. After receiving it, he claims that everything is going to plan.