118 118 Nummerjakten
The back story here is rather slim. Apparently the ghosts are out to seed chaos, their life force, by hiding the phone number 118 118 from the public.
This is an early example of a game used as a pure marketing tool, 118 118 being Sweden's leading directory assistance service at the time. In fact, an ad for Telia, the telephone company offering this service, is displayed upon the completion of each level.