Siliconera has revealed leaked prototype footage of Gotham by Gaslight, a Batman game based on the one-shot comic of the same name by Brian Augustyn and Mike Mignola and developed by Day 1 Studios, better known for their work for F.3.A.R. and Fracture.
Set in 1889 and appropriately styled in steampunk, the game would have had The Caped Crusader attempting to capture Jack the Ripper after being framed as the Ripper himself (if it follows the comic faithfully).
Day 1 Studios attempted to pitch the PS3 and Xbox 360 title in late 2009, but after THQ decided not to green light the project, its production was discontinued. In hindsight, with the success of Batman: Arkham Asylum by Rocksteady in August 25, 2009, this was probably the right decision, though this could have been a great game as well.
Hit the 1:02 mark for footage with sound.