I think that a lot of people have forgotten about the most important wonder weapon of them all. No, not the ray gun or even the Wunderwaff. I'm talking about the V-R11. This weapon is essentially the cure to the zombie virus. On a large scale, this weapon could stop the zombies. Now, in my title the reason why I said Call of the Dead is in an other dimension is that, everything is going fine as a simple movie being shot, but then the zombies come. Samantha, being a soul trapped somewhere between earth and hell, could travel between dimensions and spawn zombies. You must be asking, but why would Samantha spawn zombies in another dimension. Well don't forget, even though you don't play as them, our four heroes return as a voice between a thick metal door with a teleporter. I think that the four going through the teleporter, traveled into a new dimension making Samantha spawn zombies there.
Theory 2: My second theory (although I did not come up with it) is that Call of the Dead is in the future, and the four traveled into the future where Samantha spawned zombies there. But, once again, the movie actors were simply shooting a movie, when all of a sudden zombies come out of nowhere, and you have this wonder weapon that can turn zombies back into humans. Maybe in the future, the V-R11 is created and the zombies adefeated. Now onto the new gamemode, "Turned". I'm thinking that before the V-R11 was create Maybe they had some prototypes that didn't work right, and did the opposite of what they wanted it to do. Maybe our new cast finds the gun, and in order to follow Richtofen's orders, they must become a zombie who are under Richtofen's control.
let me know what you think!