In the giant hole in the ground, Ichabod and Abbie search for Washington's actual coffin—the grave is something of a crypt, with marble walls and multiple carvings and statues. The pyramid is the decoy and Ichabod urges Abbie not to touch it for fear it will ignite with any tampering. A few clues lead them to a chamber with Washington's body in it, housed in a coffin that looks like a senator's wet dream. It opens on its own as torches automatically light and Ichabod sees the map curled up in Skeleton Washington's hands.
They're home free except that Brooks—in a fancy new outfit that must have been inspired by The Matrix's Neo—has blocked the entrance and is coming after Abbie to obtain the map for Moloch. He practically melts Abbie's gun, throws Ichabod against the wall, and somehow causes the wall torches to fall and ignite the marble floor. Right. This leaves Abbie to defeat Brooks herself, so she plays on his love for her as an attempt to draw the real Brooks out of his demon possession. She does it for a moment and he tells her to destroy the map because Moloch needs it to win the war. Then he asks if she ever felt anything for him, would she please release him. She pokes demon Brooks in the head with a pipe and somehow totally defeats him like so many party balloons. Way. Too. Easily.
With the exit still blocked, they find a back away out, but not before the Demon half of Demon Brooks rises and comes after them. Remembering the tampering equals booby trap rule, Abbie shoots the lever on the pyramid-shaped decoy grave and causes the cavern to cave in on Demon Brooks. She, Henry, and Ichabod escape and Abbie conveys Brooks' message: destroy the damn demon map.
Ichabod is wary—this is the only lead he's had on finding Katrina all season—but she promises she'll help him find another way to save Katrina and he burns the map. In turn, he promises that they will not betray each other as the prophecy says because they have free will.
The problem with that rosy solution and display of friendship is that Ichabod has that pesky photographic memory, so that when he's home alone, crying over Katrina, he just reaches into that well and draws the map he promised Abbie he'd destroyed. Could Ichabod really be as weak as Abbie fears?