They discovered a quarry filled with walkers that could have posed an enormous threat to their community and had almost successfully lured the herd far away-but after someone destroyed the plan by drawing them back to Alexandria with a loud honking horn things will become more dangerous than ever before on The Walking Dead.

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Rick (Andrew Lincoln) and his group managed to team up with the rest of the Alexandrians to successfully try and lure the walkers to a spot 20 miles away, but at the last minute, a car horn was honked incessantly from within Alexandria's walls-drawing the herd of thousands back towards the community.

Now, in a preview clip for the October 18 episode, the danger that the herd poses to the community becomes much more real, as walkers begin to penetrate the community's weak walls.

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"I saw them from upstairs, they're coming in from all over," Carl (Chandler Riggs) says to Carol (Melissa McBride) in the clip.

"You need to stay here and keep Judith safe," she warns as she runs out the door of the house.

Sure enough, things do become dangerous and everyone is on high alert as they try to prevent a mass attack-with Maggie (Lauren Cohan) and others on the move and shooting their guns in an effort to keep things under control, and others becoming critically injured in the process.

However, the biggest threat appears to come to Jesse (Alexandra Breckenridge) and her family, as they take refuge in a closet during what seems like an invasion on their home in particular.

The Walking Dead airs Sundays at 9 p.m. on AMC.

Tags: The Walking Dead AMC television