Chainsaws Don't Kill People; People Kill People
Mary and Nerd run off the hatchway into the yard. They run and run, followed by Eddieface, who somehow managed to get by the obstacle of a wooden door locked with a wooden bar that they placed in front of his chainsaw-having self. Mary drags Nerd into an abandoned house and they put a couch in front of the door. Much like everything else placed before Eddieface, the couch is quickly ripped to shreds and he gains entry. Meanwhile, Mary's just discovered that she managed to get herself and Nerd into a house with no escape route; the windows all have bars on them and the doors are boarded up. She hides Nerd in a closet and tucks herself into a corner.
Eddieface enters the room; Mary sees him through a hole in the wall. Most of this scene is what you saw in the trailers for this movie. I found Mary's loud, heavy breathing as annoying then as I do now. Mary pushes a rat off her legs and it squeaks, which gets Eddieface's attention. Mary looks out the hole again, but he's not there.
That's because he's right behind her. Eddieface punches through the wall and grabs Mary. He then drags her through the wall and into the middle of the room and prepares to slice her in half, but Nerd runs out of his hiding place to stop him. He pushes Eddieface, who drops the chainsaw. Unfortunately for Mary, he drops it right next to her face. Awesome. She's going to die. She screams at the chainsaw for a while, apparently believing that if she expels enough air from her mouth with great enough force, it will be enough to fend off the weapon. Then she remembers that, unlike most of the cast, she has two full legs, and stands up. She half-heartedly tries to help Nerd fight Eddieface and is quickly pushed against a wall, from the relatively safety of which she can watch Nerd lose his fight with Eddieface, get hung by his handcuffs from a chandelier, and then get cut in half, from the groin up. Poor Nerd.
Mary runs out of the house, followed by Eddieface. Say what you will about him -- Eddieface is one determined guy with a work ethic to match! There is running and more running. Some of the running is in slow motion; some of it isn't. Finally, Mary comes to a fence, which she jumps over. Eddieface decides that he's so cool that he can walk through it. Unfortunately for him, the laws of physics decide to make their first and only appearance in this movie, and Eddieface trips over the fence and falls over, putting a chainsaw-sized gouge in his leg along the way. He whines about that for a while.