The plane was plummeting down so sharply vibrations were juddering through the whole fuselage; when it banked again at the last minute, the evasive action was so extreme Fallow feared the wings would be torn off. Then, bizarrely, the plane was soaring up at an angle that was just as acute. Fallow was pressed back into his seat until he felt he was on the verge of blacking out.

"It can't take much more of this punishment," he choked.

Just as he was about to prepare himself for the whole plane coming apart in midair, it levelled off. Fallow burst out laughing in hysterical relief, then raged, "What the fuck was that all about?"

Irvine pitched forward and threw up over the back of the seat in front; he tried to get his hand up to his mouth, but that only splattered the vomit over a wider area. Fallow cursed in disgust, but the trembling that racked his body didn't allow him to say any more.

One of the stewardesses bolted from the cabin, leaving the door swinging so Fallow could see the array of instrumentation blinking away. She pushed her way up to a window, then exclaimed, "My God! He was right!"

The whole planeload turned as one. Fallow looked passed Irvine's white, shaking face into the vast expanse of blue sky. The snowy clouds rolled and fluffed like meringue, but beyond that he could see nothing. Then, out of the corner of his eye, he noticed a shadow moving across the field of white. At first he wondered if they had narrowly avoided a collision with another plane, but the shadow seemed too long and thin; it appeared to have a life of its own. There was a sound like a jet taking off and then the colour of the clouds transformed to red and gold. A belch of black smoke was driven past the window.

Fallow rammed Irvine back in his seat and craned his neck to search the sky. Beside and slightly below the plane, flying fast enough to pass it with apparent ease, was something which conjured images from books he had read in the nursery.