I may, someday, in some medium, write out a whole plot/fanfiction of the cancelled Thief 4 called "Dagger of Ways" set in a modern, American version of The City from Thief. This plot could later be used by mappers to create their own map in The Dark Mod/Thief 2 Engine, if they wish.
So far, all we know so far was Dagger of Ways Garret had Keeper parents who were "disappeared" by the Keepers for trying to escape the organization for becoming too cultish. His little sister was taken and trained as a member while he managed to escape. He survived as a criminal on the streets, and now is an independent thief for hire, who has connections with the mob.
Dagger of Ways would have had 3 main factions, the Keepers who wanted to bring magic back into the world for balance. The Church, who wanted magic back so they could be the only ones who control it and can scare people back with demon attacks into giving power to the church. And the Openers, a mysterious cult who wanted magic to flow wild and had "Constantine" as a member, so presumably a more Satanic take on the Pagans.
Garret, over the course of the game, was set to be able to side with one of the factions, at the cost of the others being enraged at him. This includes his brainwashed sister in the Keepers.
The titular Dagger of Ways was a magical artifact that could let you become invisible in the real world by entering a Wraith World, where Wraith monsters would attack you if they saw you.
One mission was to take place at "Senator" Bafford's mansion, where you use a silenced pistol to take out a light, then slit a guard's throat and enter the Wraith World to sneak by another guard. You have to get by the guard, then can slice open a portal and throw him into the Wraith world where he is eaten by the monsters.
The mission continues to where Garrett gets to Bafford's basement, and comes across a hideous sight of bodies mangled and chopped up, some hanging from hooks on the ceiling. One corpse with a missing arm twitches unnaturally onto its feet and charges at Garrett, causing him to instinctively go back to the Wraith world, where he is attacked by a group of wraiths he has to pick off one by one. There was also a hidden side mission involving planting an incriminating letter for the mob in Bafford's office.