A young man and his three younger siblings, who have kept secret the death of their beloved mother in order to remain together, are plagued by a sinister presence in the sprawling manor in which they live.

In 1979 Clive Sinclair, British inventor of the pocket calculator, frustrated by the lack of home investment in his project,the electric car, also opposes former assistant Chris Curry's belief that he can successfully market a micro-chip for a home computer. A parting of the ways sees Curry, in partnership with the Austrian Hermann Hauser and using whizz kid Cambridge students, set up his own, rival firm to Sinclair Radionics, Acorn. Acorn beat Sinclair to a lucrative contract supplying the BBC with machines for a computer series. From here on it is a battle for supremacy to gain the upper hand in the domestic market.