[2][3][4] The game's player follows the daily routine of the main protagonist, John (played by Adam Brown), who grew up in a fallout shelter in Britain following a nuclear war.

John returns to level 1 to perform first aid on his arm, and quickly learns that the contaminated backup air filtration system is slowly spreading radiation throughout the entire bunker.

Intent on protecting her son, Margaret tricked John into planting poison in the bunker's ventilation system while they themselves took shelter in a sealed room, killing all of the staff except Hurley.

Horrified upon realizing the role he played in the death of the rest of the staff, John is haunted by visions their ghosts as he makes his way to the emergency exit.

For the main characters, Splendy Games hired a cast of actors including Adam Brown who had played Ori in The Hobbit film series, and Sarah Greene who played Hecate Poole in the Penny Dreadful TV series and who also voiced Anne Bonny in Assassin's Creed IV: Black Flag.

[17] GamesRadar's David Roberts lauded the game's sound design and music, remarking that "the John Carpenter-ian strains of its synths and the quality foley work help sell some of its more distressing moments...

"[20] Stephen Turner of Destructoid praised the atmospheric mood of the game, "The Bunker perfectly captures John’s sense of claustrophobia and paranoia with intense close-ups, security footage, and just a really good use of lighting.

"[22] A mixed review by Eurogamer's Christian Donlan spoke highly of the production, stating "it affords this production the means of incorporating a real Cold War bunker which, as Martin mentioned in his preview, is the true star of the show: a place both echoey and claustrophobic, and grimly evocative of old-school Britain in its range of institutional greens and greys".