Vault 112

Vault 112 is a fictional underground fallout shelter in the 2008 action role-playing game Fallout 3, created as part of the Fallout franchise by Bethesda Game Studios. Located in the Capital Wasteland setting (or an irradiated Washington, D.C. area), it is a location that the player character, the Lone Wanderer, must visit so that they can catch up to and rescue the character's father James as part of the game's main quest. It is hidden within an abandoned location called Smith Casey's garage. The vault has a relatively simple design, its central element being the multiple egg-shaped pods called Tranquility Loungers, most of which host the longtime vault residents and James in an immersive virtual reality program. In the game's lore, the vault overseer and a director of the Vault-Tec Corporation, Stanislaus Braun, oversaw the vault's virtual program experiment, exploiting it by repeatedly tormenting and killing the vault residents virtually and erasing their memories for about 200 years due to his endless sadism.

Upon entrance to one of the capsules, the Lone Wanderer is taken to a virtual world called Tranquility Lane, a 1950s-themed American dead-end street neighborhood filled with mostly unaware residents; using an avatar of a young girl named Betty, Braun takes interest in the player character and asks them to exploit the test subjects to his liking. The Lone Wanderer can choose to either follow his orders and eventually kill all the residents virtually for fun or, with hints from a self-aware woman named T. "Old Lady" Dithers, activate a program from a failsafe terminal in which AI-controlled Chinese soldiers kill them both virtually and in real life. Regardless of the path chosen, Braun will allow them and their father to exit out of the virtual reality programs and therefore the vault itself. Emil Pagliarulo, the lead designer of Fallout 3, explained that the Betty avatar and Braun's personality within it were inspired by The Twilight Zone episode "It's a Good Life", which involves an extraordinarily powerful boy who consolidates power over the residents of an isolated town with cruelty.

Vault 112 and its Tranquility Lane program have received positive attention for their dark and unsettling but sometimes humorous storyline, with writers calling the questline one of the most memorable moments of the game.