Underground Undercover Walkthrough

Underground Undercover is a Railroad Faction Quest in Fallout 4 (FO4). Read on for a full Underground Undercover walkthrough and learn Underground Undercover location and rewards.

Previous Quest	Next Quest
Tradecraft	Precipice of War

Underground Undercover Quest Summary

Underground Undercover Overview
"Infiltrate the Institute and find the Patriot and Z1-14."
Faction	The Railroad
Quest Giver	Desdemona
Quest ID	000B2D48
Rewards	・ XP: 690 ・ Railroad Rifle

Underground Undercover Walkthrough

Underground Undercover Objectives

1. Build the Signal Interceptor
2. Use the Network Scanner to Talk to Patriot
3. Find Patriot
4. Talk to Z1-14
5. Talk to Desdemona
6. File an Institute Report in PAM's Terminal
7. Head to Cambirdge Polymer Labs to Get the Password
8. Return to the Institute
9. Wait for Z1-14 to Contact You
10. Warn Desdemona

Build the Signal Interceptor

To begin, progress through The Molecular Level main quest until you reach the step where you build the Signal Interceptor. Ask the Railroad for help, and eventually, Tinker Tom will assist you in building it in any settlement of your choice.

Once ready, step inside the relay platform. Desdemona will give you this quest and a Network Scanner, which you will use later to meet Patriot.

Use the Network Scanner to Talk to Patriot

Use the terminal in the next room and load the Network Scanner Holotape. After that, upload the encrypted message and wait for Patriot's reply. Once you receive his response, read it to find out his location.

Find Patriot

Start the Institutionalized main quest to gain access to the Institute. Once you're free to roam around the Institute, you can start looking for Patriot. To find him, enter the room inside the cafeteria. At the end of the hallway, proceed to the room on the right where you'll encounter a man named Liam Binet. Speak to him, and he'll reveal that he is Patriot.

Talk to Z1-14

Liam will then introduce you to Z1-14, a Courser who also wishes to break free from the Institute's slavery. Following this introduction, Liam will ask you to obtain the Code Defender password.

Talk to Desdemona

Return to the Railroad HQ and report all your findings to Desdemona. Let her know that you found Patriot and about his request to find the Code Defender password.

File an Institute Report in PAM's Terminal

To find the Code Defender, you must first access PAM's Terminal and file an Institute Report. After that, speak to Desdemona and PAM to learn the location of the password, which will be in Cambridge Polymer Labs.

Head to Cambridge Polymer Labs

Fast travel to C.I.T Ruins and head west to find Cambridge Polymer Labs. Locate the door on the side and enter from there.

Locate the Clean Room Terminal

Inside, head to the room on the right and continue towards the center to find the Clean Room Terminal. Use it and proceed to the room across to initiate the Cambridge Polymer Labs side quest. You can ignore this for now and focus on obtaining the password first.

Return to the rooms where the quest started and continue moving until you reach a large middle room.

Hack the Terminal at the Second Floor

Head to the second floor by climbing the stairs and jumping the ledge. Enter the room by hacking the terminal to open the security door. Once opened, defeat the ghoul inside to freely obtain the password from the terminal.

Hacking Explained: How to Hack Terminals

Issue an Emergency Override

After obtaining the password, issue an Emergency Override using the same terminal to unlock all the doors blocking the exit. You can find this option by selecting the Facility Defense System from the main menu of the terminal.

This action will also make Molly hostile, attacking you as you exit the room. Defeat her to also end the Cambridge Polymer Labs quest as you exit. Make your way back to the Railroad HQ and report back to Desdemona.

Return to the Institute

When you return to the Institute, speak to Liam again to start his plans to escape by giving him the Code Defender password. Afterward, talk to Z1, and he'll request a day before providing his answer about the plans to fight for his freedom. On the next day, Z1 agrees with the plan and has successfully gathered enough rebels to fight alongside him.

You'll have an optional objective to deposit as many weapons as you can for them in a storage room just across from Liam's location.

Defeat the Guards at the Tunnel

If you don't have enough, simply proceed to the tunnel he mentions and defeat all the guards inside. After eliminating the guards, report back to Z1 and continue working for Father in the meantime. This means you'll have to complete a couple of Institute faction quests before moving forward.

Wait for Z1-14 to Contact You

After completing at least the four Institute faction quests, wait for at least a day until Z1 contacts you. You can simply pass the time by waiting on a bench or sleeping in your bed.

After that, Z1 will send a synth to you, summoning you to your room for a private conversation. You'll learn that the Brotherhood is planning to ambush the Railroad, and you'll have to warn Desdemona as soon as possible.

Warn Desdemona

Head back to the Railroad and warn Desdemona about the Brotherhood's attack. To prepare, she'll give you the Railroad Rifle, officially ending the quest. Shortly after, you'll immediately start 'Precipice of War' as the Brotherhood launches their attack.

Previous Quest	Next Quest
Tradecraft	Precipice of War

Underground Undercover Location

Where to Start Underground Undercover

Map View	Any Settlement
Quest Giver	Desdemona

All Settlement Locations

Fallout 4 Related Guides

All Factions List

List of All Factions

All Joinable Factions
Minutemen	Brotherhood of Steel
The Railroad	The Institute

Full Railroad Questline

The Railroad Quests
1	Road to Freedom ☆Freedom Trail Code☆
2	Tradecraft
3	Underground Undercover
4	Precipice of War
5	Rockets' Red Glare
6	The Nuclear Option