这里有个自称后湾沼泽幻影的变态设下一系列尸骨“艺术品”，想要将前来追查的警官吸引来并囚禁于此。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.
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 scaffold 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 is also 2 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 "xx" 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 left hand side.
Shortly upon entering the corridor, the path forks in two directions. The left hand fork leads to a dead end, blocked by a grate. However, there is a mattress at the top and several items of food in a shopping cart. Heading straight on, then turning left leads out 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 ones left there is 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 2 mannequins and a skeleton on a pallet at the far end with a chair and side table before the,. On the table is the next dear detective holotape and a 10mm pistol. Make a turn u-turn and continue through corridor, which will open up 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 and dog kennel with a human skeleton can found inside. Continue past this and turn left at the top, where the final corridor can be seen at the far end.
Upon exiting the corridor, one is in a maintenance area containing several feral ghouls and a glowing one. There are several side rooms in here, the first room, which is due to 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.
- 親愛的刑警1/2/3/4 - 四卷散落在下水道裡，後面都會有一個x標記在牆上。(詳見下方圖片區)
- A flamer - In a hidden alcove behind the glowing feral ghoul, behind a chain fence.
- 今日開鎖第2冊 - 最終區域中上述第四卷卡帶的所在位置。
- 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.
- A Vault-Tec lunchbox is at the opposite end of the tunnel from the skeleton with the fishing rod. It is in the water just past the metal ramp in a cluster of three blue crates. It may be underwater. A second one is 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.
- 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
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.