Six, a nine-year-old girl in a yellow raincoat, awakens from a dream of a woman wearing a kimono and a Noh mask. Armed with only a lighter, she sneaks through the bowels of the Maw, a massive, underwater iron vessel designed for much larger inhabitants. Throughout the Maw, she encounters several Nomes: small, skittish creatures that either flee from her or passively observe her efforts. She has the option to hug the Nomes, should she get close to one. In the Prison, where captured children are held, Six evades the carnivorous Leeches that infest its depths and artificial eyes that will turn her to stone if she is caught in their lights. Six also regularly experiences debilitating bouts of hunger; whenever she eats, a shadowy, flickering version of herself appears. After eating some bread offered by an imprisoned child, Six is captured by the blind, long-armed Janitor when he lures her into a cage with a piece of meat. She escapes but makes no effort to help the other captured children. She falls into a room filled with piles of shoes and evades the unseen monster burrowing underneath. The Janitor eventually corners Six, and she severs his arms with a collapsing door.

Caught by another bout of hunger, Six is forced to eat a live rat. She travels to the Kitchen, where children wrapped up in paper are being sent. Here, the grotesque Twin Chefs are preparing a large feast and pursue Six whenever they spot her. She makes her way outside to the hull of the Maw, above the ocean waves. Scaling the hull, Six witnesses a procession of obese, suited Guests marching into the Maw from their vessel. They lumber into the Japanese-style Guest Area, where they gorge themselves with food. The feast is overseen by the mysterious Lady from Six's dream, the masked proprietress of the Maw. Several Guests scramble after Six, but she outruns them. When she has another hunger attack, a Nome offers her a sausage. However, Six eats the Nome instead.

Six follows the Lady up into her Quarters, which are strewn with broken mirrors. Pursued by the Lady, Six finds an unbroken mirror, which she uses to repel the Lady when she tries to ambush her from the shadows. The sight of her own reflection causes the Lady pain and eventually subdues her. As the Lady lies defenseless and weakened, Six experiences a final hunger attack. She bites the Lady's neck, killing her and absorbing her magical powers. Six walks back through the Guest Area, surrounded by a dark aura. Some of the Guests try to eat her, but their lives are instantly drained and their necks snapped by her new powers. She passes through a door and proceeds up a staircase and out into the sunlight, while all the Nomes she has hugged gather at the open doorway.

In a post-credits scene, Six waits by the entrance of the Maw while a foghorn is heard in the distance.

Cốt truyện DLC

Secrets of the Maw

A trio of DLC levels that offer a "different perspective on Six’s adventures" was planned. The first one was released in July 2017,[3] the second in November 2017, and the last in February 2018.[4][5]

The Depths

A young boy, known as the Runaway Kid, wakes up from a nightmare involving him swimming in darkness before being dragged underwater. After leaving the Nursery, he follows a girl who is also fleeing, but she disappears, leaving only her flashlight behind, which the Runaway Kid takes.

The Runaway Kid finds himself in the Depths of the Maw, which are heavily flooded, and he has to avoid Leeches and make his way across by hopping on floating platforms. The Depths turn out to be the home of the Granny, who swims underwater and attempts to grab the Runaway Kid either by bumping and destroying the platforms he stands on or snatching him if he is in the water for too long. After pushing a plugged television set into the water to electrocute and kill the Granny, the Runaway Kid leaves the Depths but is caught by the Janitor. The final scene shows the Runaway Kid in a cage next to other trapped children, including Six. The Janitor pulls the Runaway Kid's cage away, paralleling Six's story just before she wakes up in her cage.

The Hideaway

The Runaway Kid escapes from the paper he is wrapped in, which is ascending on a hook towards the Kitchen, and he falls to a new level of the Maw. He finds an engine room where the Nomes are brought to throw coal in the furnace. After evading the Janitor and finding various Nomes, the Runaway Kid uses them to power up the furnace. The bucket elevator in the engine room becomes fully functional and lifts the Runaway Kid up to a furnace room where the Nomes are gathered, their shadows cast by the furnace's light resembling children. After leaving through a crack in the wall, the Runaway Kid finds himself on top of a rising elevator in which the Lady is standing.

The Residence

After leaving the elevator, the Runaway Kid enters the Lady's Residence. After solving a series of puzzles to find three missing statues while fighting off the Shadow Children, he finds the Lady looking at herself in a mirror, her unmasked face in the reflection revealed to be gruesome and deformed. The Lady is alerted to the Runaway Kid's presence and transforms him into a Nome. He then finds his way into the Guest Area and the room with the sausage in Six's story. The chapter ends with the Runaway Kid standing by the sausage, indicating that he is the Nome whom Six eats. When the credits for Secrets of the Maw roll, they are eventually shown to be on a television set, which shows a figure reminiscent of the Thin Man.