Here’s a pop trivia question: How many different kinds of zombies are there? If you’re Rick Grimes, the answer would be “One: the hungry kind.” If you’re Episode 2 director Michelle MacLaren, however, the answer is slightly different. In this new behind-the-scenes video for The Walking Dead, MacLaren gives a guided tour of the set, explaining the different classes of zombie (Alpha, Beta, Charlie and Delta) and describing how one goes about filming an undead attack in the middle of a torrential downpour.

Click here to read a Q&A with Michelle MacLaren for The Walking Dead