Our narrator gets sent home from work early because his pants are covered in dried blood. Sounds about right.
At home, all he can do is listen to the sound of Tyler and Marla boinking away.
When they're done, Marla comes down to the kitchen, sits at a table, and burns her arm with a cigarette while insulting herself. We've heard of having a cigarette after sex, but… um. Tyler says that they need to make soap in order to wash the blood-stained pants, so our narrator sends Marla to the store to buy some lye.
Before she leaves, she says all sorts of weird things about love, abuse, and abandonment.
While they wait for Marla to return, the guys have to render fat in boiling water. Tyler just happens to have a few handy baggies of fat in the freezer. Who doesn't?
As they boil fat, Tyler and our narrator talk about what it really means to hit bottom. "Only after disaster can we be resurrected" (8.85). Deep.
Marla drops off the lye and leaves, pleading to our narrator to call her later.
He gets her out the door as fast as possible and returns to Tyler.
Tyler gives him a lesson: apparently making soap and making dynamite are actually quite similar. Who knew?
Then, to show him what it's like to hit bottom, Tyler decides to give our narrator a chemical burn.