Gamache looked closely. He’d taken that area for a shadow. On snow, in certain angles and lights, shadows were blue. But not, perhaps, this particular shade. Now that he looked more closely he recognized it and almost groaned. He should have seen it right away. They all should have.

The murderer could only have created a puddle in two ways. Melt the ice and snow that was there, or spill some new liquid. But if he spilled some coffee or tea or a soft drink it would freeze in very little time.

What wouldn’t freeze?

Something specially designed not to.

Anti-freeze windshield washer fluid. The ubiquitous light blue liquid everyone in Canada poured by the gallon into their cars. It was designed to be sprayed onto the windshield to wipe away the slush and salt. And not to freeze.

Was it that easy?

‘It’s windshield washer fluid,’ said Lacoste.

Apparently so, thought Gamache. At least something about this case was straightforward.

‘How did the murderer spill washer fluid there without being seen?’ Lacoste asked.

‘Well, we don’t know that the murderer wasn’t seen,’ said Gamache. ‘We haven’t asked that question. And someone was sitting right beside Madame de Poitiers. That person might have seen.’

‘Who?’ Beauvoir asked.

‘Kaye Thompson.’ Now Gamache got up and walked to the drawing Beauvoir had made of the scene of crime. He told them about his interviews of the day before then he drew three Xs clustered round the heat lamp.

‘Lawn chairs. They were meant for the three elderly women who brought them, but only one ended up using a chair. Kaye Thompson was sitting in this one.’ Gamache pointed to one of the Xs. ‘The other two women were curling and CC sat in the chair closest to the lamp. Now this chair,’ he circled the chair closest to the curling rink, ‘was on its side. It’s also the one with the fluid under it, am I right?’ he asked Lacoste, who nodded.

‘It’s in the lab being tested but I suspect we’ll find that the chair was the murder weapon,’ she said.

‘But wasn’t the heat lamp?’ one of the agents asked, turning to Beauvoir. ‘I thought you said the victim touched the thing that was electrified. That’s the heat lamp.’

‘C’est vrai,’ Beauvoir conceded. ‘But it appears that wasn’t what killed her. The chair did, we think. If you look at the wounds on her hands, they’re consistent with the aluminum tubing at the back of the chair.’

‘But how?’ one of the technicians asked.

‘That’s what we have to find out,’ said Beauvoir, so wrapped up in the mystery he failed to tell the technician to get back to work. She’d asked the right question. How did a charge get from the heat lamp to create an electric chair?

An electric chair.