Underground Undercover Underground Undercover is a Railroad main quest and an achievement / trophy in " Fallout 4 " . Detailed walkthrough . After the Sole Survivor gets into the Institute , the Railroad wants them to make contact with an anonymous person inside , nicknamed Patriot , who has been helping synths escape . Tinker Tom provides the encrypted message holotape that will upload a message for Patriot to the Institute ' s network in the hopes that Patriot sees it and comes forward to identify themselves . After uploading the message , Patriot sends a message back telling the Sole Survivor to meet him in a maintenance closet . Patriot turns out to be Liam Binet , an Institute scientist and son of Alan Binet , the head of the Robotics department . Liam expresses surprise that anyone decoded the messages he was sending out with each synth he freed and were then able to contact him back , and he is excited at the prospect of coordinating with the Railroad . He introduces the Sole Survivor to a synth named Z1 - 14 who has been working with him to help synths escape . They discuss how many synths are ready to leave and propose a plan to free all thirteen at once with the Sole Survivor ' s help . To escape , Liam will need to bypass SRB electronic security to open some doors , but he isn ' t able to crack it . Instead , he requests a pre - War admin password from the surface . He recommends asking the Railroad for any leads on where to find one . It should be noted that the player must complete the quest Institutionalized at this point in order to be able to leave the Institute compound . The Sole Survivor returns to Desdemona at Railroad HQ and is instructed to enter their mission report in the terminal in P . A . M . ' s office . P . A . M . analyzes the data and recommends that the login credentials for Wilfred Bergman may be found in Cambridge Polymer Labs . Desdemona instructs the Sole Survivor to retrieve it while they consider Liam ' s plan . The password can be found in the laboratory section of the building on the second floor . In order to access it , however , the quest Cambridge Polymer Labs must be completed before escape from the building is possible . Looking over Liam ' s plan , Desdemona concludes that if it is successful , it may never be possible for Liam to free another synth ever again due to the Institute going on high - alert following such a security breach . She proposes instead that they should use this opportunity to free every synth in the Institute . To do that would require the synths themselves to rise up and fight for their freedom , instead of operating in the shadows . She instructs the Sole Survivor to give Liam the password he requested , but then to cut him loose and coordinate with Z1 - 14 instead from then on . Back in the Institute , the Sole Survivor gives Liam the password , then meets with Z1 - 14 to discuss Desdemona ' s proposal . He agrees with the plan and asks for 24 hours to ensure that it is possible . He speaks with the other synths and is surprised at how many volunteers he receives . They will need weapons , however , so he requests that the Sole Survivor aids them by killing a few guards so they can stage a construction accident , allowing a few synths to go into hiding in order to construct weapons . The Sole Survivor may optionally offer to provide additional weapons , which Z1 - 14 instructs to be placed in a maintenance closet . The guards are in a maintenance tunnel between Synth Retention and Robotics . After they are dispatched , the worker synths will give their thanks and collapse the tunnel after the Sole Survivor departs . Speaking with Z1 - 14 , he gives his thanks as well and states that they need time to prepare . In the meantime , the Sole Survivor should keep working with Father until they are ready . At this point the quest is put on hold until the Institute orders the Sole Survivor to take on the Railroad during End of the Line . After meeting with the Directorate , a runner will arrive in the meeting room with a message from Z1 - 14 that the Sole Survivor ' s quarters have flooded and they are needed there immediately . When they arrive , Z1 - 14 states that he ' s discovered that the Brotherhood of Steel have found the Railroad HQ and are preparing to attack , so the Railroad needs to be warned as soon as possible .