‘Dr Harris hasn’t seen a death by low voltage in more than ten years. The automatic shut-offs put an end to that. She says it’s almost impossible.’

Now he had everyone’s attention. Even the technicians, so busy in their work a moment earlier, had slowed down and stopped to listen.

A near impossible murder.

Doughnuts and coffee were arrested on their way to mouths, photographs were laid on the table, breathing seemed to have stopped.

‘Almost,’ repeated Beauvoir. ‘A number of things had to come together for this to work. CC de Poitiers had to have been standing in a puddle. In the middle of a frozen lake at minus ten Celsius she had to be standing in water. She had to have had her bare hands come in contact with something that was electrified. Bare hands.’ He brought his hands up, as though perhaps the homicide team needed the reminder of what hands looked like. ‘Again, in freezing cold temperatures she had to have taken off her gloves. She then had to touch the one thing in the whole area that was electrified. But even that wasn’t enough. The current had to travel through her body and out her feet, into the puddle. Look at your feet.’

Everyone looked at him.

‘Your feet, your feet. Look at your feet.’

All faces disappeared below the table, except Beauvoir’s. Armand Gamache bent down and looked at his boots. They were nylon on the outside. Inside there were layers of Thinsulate and felt.

‘Look at the soles of your feet,’ an exasperated Beauvoir said.

Down they went again.

‘Well?’

‘Rubber,’ said Agent Isabelle Lacoste. Beauvoir could tell by her clever face that she understood. ‘Pre-formed rubber with ridges for traction, so we don’t slip on the ice and snow. I bet we all have rubber soles.’

Everyone agreed.

‘That’s it,’ said Beauvoir, barely able to contain himself. ‘We’ll have to call round to confirm, but I bet there isn’t a boot sold in Quebec that doesn’t have rubber soles. That was the final element, and maybe the most unlikely in a series of unlikely events. Had CC de Poitiers been wearing boots with rubber or even leather bottoms she wouldn’t have died. She grabbed onto something metal. Metal conducts electricity. The earth conducts electricity. Our bodies conduct electricity. According to Dr Harris, electricity is like a living thing. It’s desperate to stay alive. It races from one form to another, through the metal, through the body, and into the earth. And along the way it races through the heart. And the heart has its own electrical current. Amazing, isn’t it? Dr Harris explained all this to me. If the electricity goes right through the body it only takes a few seconds to affect the heart. It screws up the normal rhythms and causes it to’ – he checked his notes – ‘fibrillate.’