In the third season of 3Hz, the Walkman no longer tunes into the past, but into the future. Felix and his friends discover that in 2043, their village of Roegerhout will be expropriated and completely erased to make room for a new green power plant. Even their beloved swimming pond will disappear. Although the future shows that the friends are still close years from now, it also reveals fierce protests and a community fighting for its survival. Shocked by what they hear, Felix, Ella, Sammy, and Noor launch an investigation in the present to find out why Roegerhout must vanish.

Their search leads them to the forests surrounding the village, where they stumble upon a large, mysterious building hiding an underground laboratory. There, scientists Professor Jolien Dewit and Luca Rossi are conducting research into nuclear fusion as a sustainable energy source. While the project initially seems promising, the friends uncover a troubling truth: a dangerously failed experiment involving an extremely powerful magnet lies beneath Roegerhout. Too unstable to move and capable of causing massive disruption, the magnet is being concealed by plans to build the power plant on top of it.

Determined to save their village, the friends must work together, using clues from their future selves to prevent a disaster and change what lies ahead.