Part of it resembed a bird and part a serpent: scales glinted like metal in the morning sun on a body that rippled with both power and sinuous agility, while enormous wings lazily stroked the air. Colours shimmered across its surface as the light danced: reds, golds and greens, so that it resembled some vast, brass robot imagined by a Victorian fantasist. Boned ridges and horns rimmed its skull above red eyes; one swivelled and fixed on Fallow. A second later the creature roared, its mouth wide, and belched fire; it seemed more a natural display, like a peacock's plumage, than an attack, but all the passengers drew back from the window as one. Then, with a twist that defied its size, it snaked up and over the top of the fuselage and down the other side.

Shock and fear swept through the plane, but it dissipated at speed. Instead, everyone seemed to be holding their breath. Fallow looked around and was astonished to see that faces that had earlier been scarred with cynicism or bland with dull routine were suddenly alight; to a man or woman, they all looked like children. Even the stewardesses were smiling.

Then the atmosphere was broken by a cry from the aft: "Look! There's another one!"

In the distance, Fallow saw a second creature dipping in and out of the clouds as if it were skimming the surface of the sea.

Fallow slumped back in his seat and looked at Irvine coldly. "Everything will be back to normal in a few days," he mocked in a singsong, playground voice.

May 2, 11 a.m.; Dounreay Nuclear Power Station, Scotland:

"I just don't know what they expect of us!" Dick McShay said frustratedly. He threw his pen at the desk, then realised how pathetic that was. At 41, he had expected a nice, easy career with BNFL, overseeing the decommissioning of the plant that would stretch long beyond his life span; a holding job, no pressures apart from preventing the media discovering information about the decades of contamination, leaks and near-disasters. Definitely no crises. He fixed his grey eyes on his second-in-command, Nelson, who looked distinctly uncomfortable. "I have no desire to shoot the messenger, William, but really, give me an answer."