So the gang heads to Bannerman Island, the site of one of Washington's old military prisons. Hope he's not tortured by ghosts of all the Redcoats his men incarcerated. Just as the gang suspected, it also houses G.W.'s true tomb; suck it, Mount Vernon! After much National Treasury -- a pyramid marked "I.M." for "the indispensable man"; a telling relief of Cincinnatus; a crack on the wall just large enough for a Masonic ring -- they've got their hands on the map, perfectly preserved after all these years. And with time to spare, too!
Scratch that: We've got company. Earlier in the episode, Zombie John Cho tried to get Abbie to switch to his side, promising her "a high seat in [Moloch]'s new order" and swearing that nobody's ever loved her the way he does. When she told him to get lost, he slunk back to his master, who encased Zombie Cho in a cocoon of evil. Now he's emerged as a slimy hellbeast with an alien head, pure black eyes, and a thirst for vengeance that could only be a consequence of serious Nice Guy Syndrome. Just call him the worst parts of Reddit personified. (Demonified?)
Our heroes just manage to escape with their lives, destroying Washington's tomb (and leaving Zombie Cho stuck in its ruins) in the process. After all that, Abbie opines that if Moloch wants the map this badly, they should probably just destroy it. Ichabod is clearly conflicted; after all, this scrap of paper holds the key to rescuing his lost love. But in the end, he agrees with Abbie, burning the map to cinders...
...except, wait. Remember how Ichabod has a photographic memory? Because Ichabod does.
As the night's second episode begins, Abbie is none too pleased that Ichabod neglected to mention he memorized the map. But she's not complaining about his deception when Henry shows up at the cabin, informing the Witnesses (and Jenny, who's stopped by for some morning snark) that Moloch plans to raise the Second Horseman of the Apocalypse that very night. The only thing capable of stopping him is a binding spell, which must be cast by a witch... meaning that it's finally time for Ichabod and Abbie to make the descent all of season 1 has been leading toward.