Slap bang on the border between the known universe and the realm of anti-matter lies the planet of "Zeta Minor". That's where the "Doctor" (Tom Baker) and "Sarah Jane" (Elisabeth Sladen) have to go to answer a distress call - and where they discover a professor "Sorenson" (Frederick Jaeger) who thinks he's found the ultimate solution to the energy crisis. Sadly, though, when they try to leave the planet they go nowhere fast. It seems that this energy has no intentions of leaving it's home world. Indeed, the more exposure the scientist has to this power source, the more malevolent it's influence and the more maniacal he becomes. Meantime, the ship's captain "Salamar" (Prentis Hancock) is proving to be hopelessly inadequate in a crisis and the crew are relying more on "Vishinsky" (Ewen Solon) and the time travellers to find a way to get them to safety. The stage bound production here isn't the best, but the quite effective visuals are straight out of "Forbidden Planet" (1956) and this is a solid story that allows the now entirely confident Baker to parade through the four parts with mischief and an enjoyable joie de vivre. Good fun.