Inside, a serial killer dubbed the "Fens Phantom" has built a menagerie of horrors to portray his kills to an unnamed detective on his trail. Following the holotapes left by the murderer, the Sole Survivor can learn about the killer's interest for the detective, leading to his ultimate demise or capture.
Access to the sewers is gained via a manhole to the north of Diamond City. Take the exit to the west of the main gate and head north, turning west at the scaffolding ramp into a side alley. The entrance is surrounded on 3 sides by railings, within their confines is the manhole cover, a toolbox, and a skeleton.
Upon entering, turn right at the end of the short corridor, where one can see a skeleton trussed from the ceiling with an "x" etched on the wall. Next to this a side cabinet with a toy car, toy rocketship and the first dear detective holotape set on the top. There are also two wooden blocks and a toy truck on the lower shelves. Looking to the right while approaching the skeleton, a skull and arm can be seen protruding from the wall.
Turning right from the cabinet and heading down the slope, the area opens up into the sewer itself. On the left a headless skeleton is set on the wall arch, propped up by a toolbox, holding a fishing rod and a skull fixed to the hook. Below the pelvis "xxx" has been etched onto the wall. Head down into the water and turn right, following the flow of the water, which contains three feral ghouls. Halfway along the sewer path here, one can see a skeleton on the floor between a toolbox and a radio. Just above them, there is a single "x" on the wall.
Exit the water from the ramp at the end and follow the path through the narrow pathway, veer to the left and a skull can be seen on a barbecue, next to the second dear detective holotape. Looking to the west of this display there is a cooler and a makeshift battery. Turn back to the east and head left upon reaching the far wall. Follow the pathway into another sewer section, making a right turn in order to head down the stairwell and into the water, which contains several barrels and two bloatflies. Take the steps up to the far left and head through the corridor on the lefthand side.
Shortly upon entering the corridor, the path forks in two directions. The lefthand fork leads to a dead end, blocked by a grate. There is a mattress at the top and several items of food in a shopping cart. Turning left heads into the next section of the sewers. Upon entering this section, one will see a cymbal monkey and a skeleton with a brahmin skull wearing a bowler hat set on the ledge. Glancing to one's left there are five baby strollers.
Head over the bridge and up the slope, turning right and following the wall into a new corridor. At the end of this corridor is a gas-filled room with two mannequins and a skeleton on a pallet at the far end with a chair and side table. On the table are the next dear detective holotape and a 10mm pistol. Turning will lead into the upper section of the room with the strollers. Head up the ramp and follow the pathway to the right. Partway up the wooden steps, a dog kennel with a human skeleton can be found inside. Shortly the final corridor can be seen at the far end.
Upon exiting the corridor, there is the maintenance area containing several feral ghouls and a glowing one. There are several side rooms here, the first room, which is due south from where one enters the area contains the final holotape, a copy of Tumblers Today and an Expert locked safe. To the far west of the main room is a red steamer trunk. heading up the stairs and following the winding linear path will lead back into the room with the skeleton fishing with a skull.
- Four audiologs, the dear detective tapes - Along the path with many dead bodies in peculiar postures. Each has a white 'X' chalk mark on the wall indicating the body count.
- A flamer - In a hidden alcove behind the glowing feral ghoul, behind a chain fence.
- Tumblers Today issue #2 - At the end of the zone near a safe and the last tape in the "cell" area.
- A Stealth Boy - Right next to the Tumblers Today magazine.
- An X-cell - In the first room near the fishing skeleton, across the water in a blue basket tucked behind a gray pipe and a blue pipe.
- Two Vault-Tec lunchboxes - One at the opposite end of the tunnel from the skeleton with the fishing rod, in the water just past the metal ramp in a cluster of three blue crates; and another in one of several baby strollers near the "XXXX" on the wall.
- A dog collar - Located around the neck of a skeleton inside a dog house towards the end of the sewer.
- Ghoul Problem: Settlers have asked the player character for help in taking care of some feral ghouls that have been terrorizing a nearby location.
- In the room with radioactive barrels in the water, jump onto the horizontal blue pipe on top of the stairs to gain access to a weapon stash near an activated radio to the left. The radio is turned on and can be heard.
- If Strong is brought here, he will speak of a time he and his brother ate a human in the sewers.
- In the last room with the skill magazine, the Sole Survivor can jump off the pathway to a small alcove with a mattress, machete and a skeleton couple. This mattress cannot be slept on. Assuming the story told in the holotapes is true (especially the fourth part), this may show the dramatic result of the detective's investigation.
The Fens Street sewer only appears in Fallout 4.
Behind the scenes
- The Fens Street sewer was created by level designer Justin Schram.
- In an inaccessible area of the sewer (you can only get there on PC with tcl), in the northwest edge of the local map just beneath the triangle on the right, a human head can be found held up by tibias. This is a reference to the "head crab spider" in the 1982 film The Thing.
- Alumni Guest: Justin Schram From Bethesda Game Studios (reference starts at 59:19)
Justin Schram: "And then also, the Fens Street sewer I just thought was a nifty little, contained...self-contained dungeon experience that I was very proud of."