On a holiday to Mt Tarawera, teenager Jenny finds an odd shard of metal. In this third episode of the kids sci-fi series she meets its owner: 'Drom' — a survivor of an alien mission to deactivate a planet-annihilating space gun (aka Tarawera itself). They find themselves under siege from a Predator-like 'Guardian' of the gun. If Drom and Jenny and local kids Tessa and Lloyd can't defeat the mechanoid, catastrophe is imminent! The South Pacific Pictures series found international sales and cult repute.

Serija počinje prikazom ekspedicije helikopterom pri čemu mlada Jenny hoda po rubu mirujućeg vulkana Tarawera pri čemu je ugledala plavo svjetlucanje pri sredini grotla. Polagano se spustila, te je ugledala oštri komad metala zabijen u vulkanski materijal. Kad ga je teškom mukom iščupala, dogodio se potres pri čemu je pala u grotlo, ozlijedivši se......