The day after, they heard by telegraph from San Francisco that a consignment of nitroglycerin which had been stored in the back of the Wells Fargo office in San Francisco had exploded for no apparent reason, killing twelve passers-by and tossing a gory arm into the street. And by the end of the week, in spite of hours of argument and wheeling and dealing in the state capital by Leland and his friends, all shipments of nitroglycerin into California were indefinitely suspended. Collis was furious.

Alone, he took out a buggy and drove back along the roadbed as far as Dutch Flat. It was a sunny afternoon, and for the first time in months he wore a beige linen coat and a flat white hat. He reined in his horse outside of Doc Kate’s pharmacy and drugstore and stepped inside.

The place hadn’t changed at all. There was still the smell of coughdrops and soap that he remembered from the first time he had walked in with Theodore. And there behind the counter, measuring out bath salts, was Doc Kates himself.

‘Doc?’ Collis said.

Doc Kates peered at him hard through his spectacles, then smiled in recognition. ‘Collis Edmonds. Well, I’ll be. I thought you’d be sitting in a fancy office in San Francisco by now, not out here in the wilds.’

He finished serving the bath salts, and then he beckoned Collis through into his back room. ‘What would you like? Coffee, tea, or a belt?’

‘Coffee will do fine. I’ve got a hard day ahead of me.’

‘The way that railroad’s cutting its way through the mountains, I’m not surprised,’ said Doc Kates. ‘I went out to the tracks a week ago, and I could hardly believe that those rails were lying along the same old path that you and Theodore Jones pencilled down on your maps.’

‘The path that you found, Doc,’ Collis reminded him.

Doc Kates put the coffee-pot on the stove, sniffed, and wiped his hands on his apron. ‘I sure was sorry to read about Theodore in the Union. He was a fine young man. Inspired.’

‘Yes, you could say so,’ said Collis.

Doc Kates sat down. ‘Well,’ he said, ‘what brings you back to the old drugstore? You didn’t just come here to chew the fat, did you?’

Collis shook his head. ‘It’s the tunnel we’re digging through to the summit. We made very slow headway during the winter, because all we had was black powder. Then Leland McCormick brought us some nitroglycerin. Blasting oil, they call it, and that cuts through the mountain like cheese.’

Doc Kates nodded. ‘I see your problem. They’ve banned it now, haven’t they, after that big bang in San Francisco? So how are you going to blow your way through to the pass?’

Collis sat back in his chair. Through the window, he could see Doc Kates’s vegetable garden growing, just as it had last year and the year before, and always would do, until he died. ‘As far as I understand it, nitroglycerin’s made out of sulphuric acid, and nitric acid, and glycerine.’