Most infected bats only increased slightly in size, but one bat was different from all the others. This particular bat grew to an enormous size of three meters, possibly due to a unique mutation. The Giant Bat was highly aggressive and defended its territory, a church, with deadly force.

Billy and Rebecca came into contact with the Giant Bat when they entered the church near the training facility. The bat came at them with all its fury; it was even followed by a small army of normal sized bats. After a difficult battle the Giant Bat was killed, never has another bat grown to that size.