Hole in the Wall

Hole in the Wall is a side quest in Fallout 4.

Detailed walkthrough
After donating blood to Dr. Forsythe, leave the vault and either pursue the Here Kitty, Kitty quest to find Ashes or wait for 24 hours or more before returning (the player character may have to complete another quest in addition to waiting 24 hours before the next scene will trigger). Upon the Sole Survivor's return, Austin Engill will have been moved to the vault's medical bay. Speaking with Dr. Penske begins the quest.

Austin was bitten by a mole rat when wandering in a secret part of Vault 81 and subsequently fell ill. One must follow Bobby De Luca to the entrance hidden in the reactor room. They are asked to go into that part of the vault and find a cure. During the investigation, they must fight or sneak their way through run-down rooms full of Vault 81 lab mole rats, which will transmit a disease if they manage to bite the Sole Survivor, their companion or any activated Protectron, conferring a potentially permanent loss of 10 HP. The true purpose of Vault 81 as an infectious disease incubation and vaccine development facility is also discovered. In the final area, there is a terminal that must be hacked or unlocked with a password in the far room on the upper floor past a mole rat brood mother. The password to the locked terminal is next to the research comm terminal in the subsequent room. After this room the player character will find a robot named Curie who has manufactured the cure; however, there is only one dose left. Curie follows the player character out of the secret vault up an elevator back to the locked door by the main vault's entrance. The player character must then return to Dr. Forsythe in the medical bay with the cure and make a choice.

Option 1: Give Austin the cure
If the Sole Survivor gives the cure to Dr. Forsythe, they receive rewards including the syringer rifle and a room in Vault 81 located across from the depot. Most items throughout the vault are no longer marked as owned and can be freely picked up without angering the residents. As a side effect, if the Sole Survivor has contracted the disease during this quest, they keep the disease.

Option 2: Deny Austin the cure
Regardless of whether it's by directly refusing to hand over the cure in dialogue (requires selecting "Only one, it's mine" followed by "Let him die"), selling or losing the cure, or using it directly from the player character's inventory (to cure the mole rat disease which has been contracted in the secret vault), all of these options are treated the same — Austin dies and everyone in Vault 81 blames the Sole Survivor. A small memorial for Austin is prepared in the classroom under the "America lives on... in you" poster, consisting of a candle, a new teal flared vase, a toy car, a baseball glove and a teddy bear.

Either option results in the quest concluding and Curie asking to accompany the Sole Survivor around the Commonwealth in order to further her scientific research, becoming available as a companion.

Bugs

 * If any companion or any type of creature not hostile to the player character, including the hackable Protectron in the area, gets hit by one of the diseased mole rats, then the player character will get the disease as if they had been bitten instead.
 * If you leave the vault before Bobby opens the secret door, he will have gone into the secret vault with the secret door still being closed, making it impossible to finish the quest.
 * Sometimes, the cure will duplicate when picked up by the player, making it possible for the player to cure themselves and Austin at the same time.
 * Sometimes Dr. Penske will not be in the room discussing Austin's illness with Dr. Forsythe and the quest will not start.
 * This can be resolved by going to Dr. Penske's office and talking to her there to start the quest.
 * Sometimes, Bobby De Luca will try to run straight towards the quest marker and will get stuck in the room adjoined to the medical bay.
 * To fix this, head to the reactor then type into the console: . This should allow Bobby to reach the marker.
 * On console, reload an earlier save.
 * It is possible to get stuck under the stairs leading down from the overseer observation station in the secret section of the vault, requiring you to reload a save.