After evading the robots and reuniting with Athena, the trio uses a teleportation machine that Frank invented, and transport themselves to the Eiffel Tower in Paris. They enter a room with mannequins of Gustave Eiffel, Jules Verne, Nikola Tesla, and Thomas Edison. Frank explains that the four men were the founders of Plus Ultra, a group of inventors dedicated to finding other dreamers and inventors who shared the hope of shaping a better future, which eventually led them to discover a new dimension where Tomorrowland was founded. The trio enter a rocket hidden underneath the tower, which launches into outer space and after traveling through dimensions, lands back on Earth, arriving at a now desolate Tomorrowland. Nix appears to greet them, and takes them to a building linked to a tachyon machine designed by Frank himself that can show images from the past and future, from which Casey learns that a worldwide catastrophe will happen in the near future. Because of this discovery, Frank lost all hope and was banished from Tomorrowland. Casey does not accept that the world is destined to end, and the future slightly changes as a result, a fact that Frank glimpses, but which Nix ignores before ordering them arrested instead.
As they await being sent back to Earth, Casey realizes that a side effect of utilizing tachyons to obtain information about the future is that it introduces a backfeed into the time flow. It makes the future it shows all the more likely to occur, creating a self-fulfilling prophecy. Destroying the device could avert the apocalypse. Nix opens a portal to an idyllic beach dimension, inviting them to live out the last days there, but Frank refuses, seeing that Nix has simply given up on Earth and intends to allow the apocalypse to happen. A fight ensues and Frank tries to use a bomb to blow up the machine. Mistakenly, the bomb goes off outside the portal and the explosion pins Nix's leg under debris. Nix retrieves a plasma gun and aims at Frank. Athena, who was able to see it happening beforehand due to the tachyon images, jumps in front of him and is damaged beyond repair, which activates her self-destruct sequence. In her last moments of consciousness, Athena instructs Frank to take her to the machine and reveals that she loved him. Her self-destruction takes down the machine and kills Nix as well.
Back in the present, Frank and Casey's audience revealed to be androids like Athena, who are entrusted with new pins and instructed to bring other "dreamers" to Tomorrowland.