Sector 4 Sector 4 is a location on the Planet in the " Compilation of Final Fantasy VII " . It is one of the eight sectors in Midgar , and is visited briefly by the party during the events of " Final Fantasy VII " . The locations visited in Sector 4 are unrevisitable and cannot be re - explored once the story has progressed beyond them . Story . After the success of the Sector 1 Reactor bombing mission , AVALANCHE plan another mission on the Sector 5 Reactor . In the early hours of the morning after the first mission , they board a train for the Sector 4 Station . The train uses an ID scan system , making the fake IDs made by Jessie ineffective , and therefore the party plan to jump off the moving train into the train tunnel . Unauthorized personnel are discovered on board prior to when the check was meant to happen due to modifications to the ID cards made by Jessie , meaning the party has to move down the train to the end cart before the lockdown . While Cloud ' s party jumps off the train , Biggs , Wedge , and Jessie stay on board in disguises . After moving down the railway , Cloud ' s party come to Shinra ' s security sensors and have to look for another way . The party crawl through a duct into the Lower Sector 4 Plate . As Cloud ' s party move through the plate , they find the rest of AVALANCHE have made it there safely . The others withdraw back to Sector 7 as Cloud and his party enter the Sector 5 Reactor . Locations . Winding Tunnel . Multiple areas that look the same , there are six screens in total . the screen the player jumps off at depends on the point the player jumps off the train to Sector 4 . Timing out in Car # 1 has the player jump off at Tunnel 2 , in Car # 2 at Tunnel 3 , in Car # 3 at Tunnel 4 , in Car # 4 at Tunnel 5 , and making it to the end leaves the player at Tunnel 6 . The southern most tunnel , Tunnel 1 , leads to the danger area . The northern most tunnel , Tunnel 6 , leads to the security sensors . North end of the tunnels , blocked by Shinra ' s security sensors . Exit through first duct to enter the Lower Sector 4 Plate . South end of the tunnels . Shinra security guards are here . Choosing to stay will lead to an encounter against three Special Combatant s , choosing to leave will move the player onto the next screen . This can be repeated indefinitely . Lower Sector 4 Plate . Moving through the duct takes the player to the ladder room . There is an Ether on the floor . Moving down the ladder takes the player to the big room . Originally entered by going down the ladder from the ladder room . Ladder in the middle of the room leads to the crawl duct which leads to small room . The ladder on the right also leads to small room , and Wedge is standing by it . Wedge tells the player that the reactor is up the ladder he is standing by . Connected to the big room via a crawl duct at the top of the screen . Also connected to the big room via a ladder in the bottom - right . Also connected to the exit by going down a ladder on the left . A Potion is across from Jessie in the top - right of the screen . Jessie tells the player that the ID scan problem was her fault as she modified Cloud ' s ID . Connects the big room and the small room . Connected to the small room via a ladder . There is a ladder to climb up through a vent and into the Sector 5 Reactor . Further passed the ladder is a Tent item and a save point . Biggs is by the ladder . Biggs tells the player that him and his party will withdraw to the hideout . Quests . Path to Sector 5 Reactor . Sector 4 is only visited once after getting off the train to sector 4 . The only goal here is to pass through the sector and reach the next reactor .