 Though the aliens' initially appear to be humanoid bat-like creatures, they are subsequently shown to be squidlike, but ultimately revealed to be insubstantial energy-beings from a higher dimension.The novel's protagonist is Captain Olof Carlsen, the commanding officer of the space exploration vehicle which discovered the vampires' spacecraft.The novel was mildly successful and was translated into many languages including Spanish, Japanese, German, French, Italian, Dutch and Swedish.