847 people is hit by a mysterious illness, and they all see a huge mackerel hovering over the square. Everyone infected by the so-called Mackerel syndrome are from the same quarter of the city, and they appear to live in two different worlds. The therapists sent to speak with them can interact as usual, but they are also surrounded by other creatures – invisible to everyone else but themselves. Amongst the 847 people is Silas. Everyone who knows him says he is an 'especially interesting case'. He can speak to the dead. Or are they really dead?

The infected quarter is blocked with lazer barbed wire, while the rest of the society try to figure out the cause of the illness. What will the future be, for the sick and for the seemingly healhty people? Which of the realities will prevail in the end?

The Heavenly Mackerel is an entertaining, wise and imaginative science-fiction novel, by Norway's most influential author of fable prose.