The Walking Dead 2.13 - Besides the Dying Fire (season finale - SPOILERS)

[Style]

Lori was secretly slipping out at night and laying trails of chicken entrails to lead the horde to the farm. If you look carefully in the night-time shot of episode #11, you can see her at the back with a big bag of guts. It was actually her fault.

 

[Dannyalcatraz]

I figured it out: [sblock]Carl causes zombies.[/sblock]
That's why we have a zombie apocalypse in the first place.