I was tired and sleepy, and as I forced myself to think of the immediate problem, the six lines of the jingle were all blurred. While I undressed I tried to repeat them, but could not get the fourth to scan. It came out as “fields of Erin,” and after that “the green fields of Erin.” Then it became “the green fields of Eden.”

I found myself humming a tune.

It was an old hymn which the Salvation Army used to play in the Cape Town streets when I was a schoolboy. I hadn’t heard it or thought of it for thirty years. But I remembered the tune very clearly, a pretty, catchy thing like an early Victorian drawing-room ballad, and I remembered the words of the chorus—

 

“On the other side of Jordan
In the green fields of Eden,
Where the Tree of Life is blooming,
There is rest for you.”

 

I marched off to Greenslade’s room and found him lying wide awake staring at the ceiling, with the lamp by his bedside lit. I must have broken in on some train of thought, for he looked at me crossly.

“I’ve got your tune,” I said, and I whistled it, and then quoted what words I remembered.

“Tune be blowed,” he said. “I never heard it before.” But he hummed it after me, and made me repeat the words several times.

“No good, I’m afraid. It doesn’t seem to hank on to anything. Lord, this is a fool’s game. I’m off to sleep.”

But three minutes later came a knock at my dressing-room door, and Greenslade entered. I saw by his eyes that he was excited.

“It’s the tune all right. I can’t explain why, but those three blessed facts of mine fit into it like prawns in an aspic. I’m feeling my way towards the light now. I thought I’d just tell you, for you may sleep better for hearing it.”

I slept like a log, and went down to breakfast feeling more cheerful than I had felt for several days. But the doctor seemed to have had a poor night. His eyes looked gummy and heavy, and he had ruffled his hair out of all hope of order. I knew that trick of his; when his hair began to stick up at the back he was out of sorts either in mind or body. I noticed that he had got himself up in knickerbockers and thick shoes.

After breakfast he showed no inclination to smoke. “I feel as if I were going to be beaten on the post,” he groaned. “I’m a complete convert to your view, Dick. I heard my three facts and didn’t invent them. What’s more, my three are definitely linked with the three in those miscreants’ doggerel. That tune proves it, for it talks about the ‘fields of Eden’ and yet is identified in my memory with my three which didn’t mention Eden. That’s a tremendous point and proves we’re on the right road. But I’m hanged if I can get a step farther. Wherever I heard the facts I heard the tune, but I’m no nearer finding out that place. I’ve got one bearing, and I need a second to give me the point of intersection I want, and how the deuce I’m to get it I don’t know.”

Greenslade was now keener even than I was on the chase, and indeed his lean anxious face was uncommonly like an old hound’s. I asked him what he was going to do.

“At ten o’clock precisely I start on a walk—right round the head of the Windrush and home by the Forest. It’s going to be a thirty-mile stride at a steady four and a half miles an hour, which, with half an hour for lunch, will get me back here before six. I’m going to drug my body and mind into apathy by hard exercise.