Dressed in a military flak jacket and combat boots, wearing a backpack loaded with thirty pounds of sand and with an assault rifle strapped across her chest or held above her head, she ran in the sweltering heat until her legs buckled. She picked herself up and ran some more. She crawled through mud. Climbed ropes and nets and scaffolding. She trod water dressed in her SWAT clothing and tactical gear. When she removed herself from the stream, the sand-filled backpack now twice as heavy from the water, she ran until she collapsed. When the fun ended, she was treated to a boxed lunch – two bottles of water, bread and an apple – and ate it along the way to the firing range, where she shot at targets until the muscles in her forearms cramped. The training ended at 10 p.m. After a quick shower, she slumped into her cot at the all-male bunker and woke at 4 a.m. to start the process all over again.

The second phase of training, Darby knew, was also designed to break one's mental spirit. Without proper sleep, the body couldn't heal. The physical toll tore down the mind's protective walls and lead to frustration, anger and, in some cases, dementia. Two more men dropped out. They couldn't hack it. The final three made it to the live training exercise.

Haug walked quickly down the final set of stairs. Her SWAT partner lay on his back smoking a cigar, his chest and one shoulder covered with blood-red paint. He saw her and waved. The members of Haug's SWAT team who had been brought in to play the roles of Chris Flynn's bodyguards smoked cigarettes and cigars and talked among the crates and shelves. They didn't look at Haug; they were looking at her. She felt their glares drilling into her skin.

They're pissed I killed them. She grinned.

Haug stepped into the car park. Sweat had soaked through his grey T-shirt. He fitted a thick wad of chewing tobacco in the pocket of his cheek. As usual, it was impossible to read his face. The man lived behind an emotionless mask carefully crafted from his years as a marine.