He lifted the box lightly from her hands and carried it aft. She strained round in her seat, watching until it was safely placed in position. Gregor was speaking through the implant again, but his voice was almost unintelligible through the interference.

“…get to the lower floor… standing next to the street light… again…”

His final words were lost in the increasing noise of the engines. The aircraft, wide-bodied and squat, began to move along the runway. There was a sudden acceleration that pressed her back hard into the seat. They left the ground rapidly and began to climb at an angle of about thirty degrees, powering up to the cruising altitude of ninety thousand feet and a cruising speed above Mach Two.

Julia lay back in her seat, exhausted. She could not relax, but sheer physical and mental strain were taking their toll. She sat there, silent, as the liner reached its assigned altitude and set a great circle route for Capetown. The pain that she had felt when she stretched forward in her seat had not gone away. It was a dull, sullen ache in her belly, rising from time to time to a fierce cramp. But she had escaped. Whatever it was that Gregor feared so much could not reach her now.

An hour into the flight they were approaching Commonwealth Bay, on the shore of Antarctica. The pilot’s voice had just come over the passenger address system, pointing out that they were about to fly over the South Magnetic Pole. The violent explosion in the cargo hold at the extreme rear of the craft obliterated his words.

The on-board computer did its best. Milliseconds after the internal pressure dropped below a quarter of an atmosphere, radio signals were sent to the Search and Rescue satellites that monitored the Earth constantly from low polar orbit. At the same time, the computer assessed the damage to the structure of the aircraft and decided that it was not possible to make a powered descent.