Incredibles: The Subterra Files is the Survival Horror/Thriller prequel to Incredibles: Underminer's Uprising. It follows a crew of hackers, led by Aiden Pearce, who's aim is to uncover the truth behind The Underminer's supposed death and the burial of The Gilgenbot. However, when they infiltrate a Blume Corporation Building [Blume is an antagonist Faction in Watch Dogs], they quickly find that Blume is experimenting on the dead body of The Underminer [hence the disappearance of The Underminer's body when the two men, Will and Chris, found The Gilgenbot buried in ice at the start of Underminer's Uprising]. After a shootout with Blume Security after being spotted, an accidental triggering of the Emergency Activation began, in which a whole floor of the building blew up and caused the body of The Underminer to awaken and stalk the station, now more brutalizing and more powerful than ever. Unarmed and underprepared, Aiden must now sneak around the building to find out the truth about Blume, while also evading the ever-present Underminer threat.
Incredibles: The Subterra Files, unlike any other game in the series, is a Survival Horror game, as it implores mechanics based on running and hiding. There are some shooting scenes in the game, such as right at the start where Aiden and the other Watch Dog Team Members sneak through the base to get to the Research Lab. After a shootout, a huge lab explosion blows a whole floor up, knocking Aiden out and separating him from his team. After that, Aiden's only weapon is the M1A2 Revolver, which he can use to fend off The Underminer. Speaking of The Underminer, this is the first game where he is actually intimidating and scary, much like the Xenomorph Drone in Alien: Isolation.
The Underminer's AI is determined by player actions. For example, if the player [controlling Aiden] was to run, this would cause a noise that The Underminer would immediately react to, and essentially kill the player unless he/she hid in a locker or another piece of cover, making the game similar to Alien: Isolation in both AI and nerve-dropping moments of jumpscares.
The game opens up with a recap of Rise Of The Underminer, after the Gilgenbot was destroyed and Underminer was seemingly killed.
The point of view then switches to 5 months after the events of Rise Of The Underminer, in Chicago. Aiden Pearce and T-Bone are on a apartment roof as they discuss the Underminer's Invasion, and T-Bone says "So, you think Blume found the body?" and Aiden says "Yeah. When The Incredibles left, I snuck into that giant robot's wreckage. I didn't find any giant mole, though." and T-Bone responds with "So, what are you gonna do?" and Aiden says back "Contact Clara and the others, they can help us." and T-Bone says "With what?" and Aiden answers with "Infiltrating Blume." and T-Bone says "Am I high or did you just say you were gonna SNEAK into BLUME?!" and Aiden says "Just call the others, T-Bone. We need to know what happened to the body." and T-Bone sighs, before calling the rest of the team.
The game then switches to the Blume Corporation Building as dramatic music plays, and shows The Underminer being experimented on by Blume Scientists [while the Jason X Theme plays over the scene].