“And then one evening McAndrew came over to dinner. It was during the meal that I mentioned Jack’s nocturnal serenader, expecting that Mac would treat it as lightly as I did.
“ ‘Seven times you’ve heard him, Jack, haven’t you,’ I said, ‘and always the same tune?’
“ ‘Always the same tune,’ he answered quietly.
“ ‘Can you whistle it now?’ asked McAndrew, laying down his knife and fork and staring at Jack.
“ ‘Easily,’ said Jack. ‘It goes like this’—and he whistled about six notes. ‘On and on it goes—never varying——Why, McAndrew, what the devil is the matter?’
“I glanced at McAndrew in amazement; then out of the corner of my eye I saw the native servant, who was shivering like a jelly.
“ ‘Man—are you sure?’ said Mac, and his face was white.
“ ‘Of course I’m sure,’ answered Jack quietly. ‘Why?’
“ ‘That tune you whistled—is not good for a white man to hear.’ The Scotsman seemed strangely uneasy. ‘And ye’ve heard it seven nights? Do you know it, Walton?’
“ ‘I do not,’ I said grimly. ‘What’s the mystery?’