I just beat Overtime mode and now I want to get the "Rescue 50 Survivors" achievement, but to make it easier I'd like to just disregard the story missions (except maybe getting Katie Zombrex if that ends the game...?) and focus only on the side missions. Can I even do this? Thanks.

Probably, I'm in the middle of that myself, and I don't think I screwed myself over by skipping the story missions. Are there any survivors you can only pick up with the story?

Yes you can. It'll just fail and you can keep playing. At least for the story missions. I assume the game ends if you don't get zombrex, but if you're using a new game+ you should be able to afford to just buy it at a pawn shop anyway.

YEs but you wont get "the truth" but if ur just going for survives go ahead

So, can someone who has gotten the achievement confirm that you don't have to do any story missions. I'm curious if it will work since...
 

" So, can someone who has gotten the achievement confirm that you don't have to do any story missions. I'm curious if it will work since...
 

SPOILER WARNING: Click here to reveal hidden content.

The military don't actually rescue the survivors, it isn't until you call in Rebecca's news station in the last story mission that the survivors are evacuated.

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you can ignore zombrex. me and my friend missed katie we were pretty pissed since we were right at the entrance of the thing.