The trouble was the key word, and when I thought of the odd million words he might have used I felt pretty hopeless. But about three o’clock I had a sudden inspiration.

The name Julia Czechenyi flashed across my memory. Scudder had said it was the key to the Karolides business, and it occurred to me to try it on his cypher.

It worked. The five letters of ‘Julia’ gave me the position of the vowels. A was J, the tenth letter of the alphabet, and so represented by X in the cypher. E was XXI, and so on. ‘Czechenyi’ gave me the numerals for the principal consonants. I scribbled that scheme on a bit of paper and sat down to read Scudder’s pages.

In half an hour I was reading with a whitish face and fingers that drummed on the table.

I glanced out of the window and saw a big touring-car coming up the glen towards the inn. It drew up at the door, and there was the sound of people alighting. There seemed to be two of them, men in aquascutums and tweed caps.

Ten minutes later the innkeeper slipped into the room, his eyes bright with excitement.

‘There’s two chaps below looking for you,’ he whispered. ‘They’re in the dining-room having whiskies-and-sodas. They asked about you and said they had hoped to meet you here. Oh! and they described you jolly well, down to your boots and shirt. I told them you had been here last night and had gone off on a motor bicycle this morning, and one of the chaps swore like a navvy.’

I made him tell me what they looked like. One was a dark-eyed thin fellow with bushy eyebrows, the other was always smiling and lisped in his talk. Neither was any kind of foreigner; on this my young friend was positive.

I took a bit of paper and wrote these words in German as if they were part of a letter—

… ‘Black Stone. Scudder had got on to this, but he could not act for a fortnight. I doubt if I can do any good now, especially as Karolides is uncertain about his plans. But if Mr T. advises I will do the best I …’

I manufactured it rather neatly, so that it looked like a loose page of a private letter.

‘Take this down and say it was found in my bedroom, and ask them to return it to me if they overtake me.’

Three minutes later I heard the car begin to move, and peeping from behind the curtain caught sight of the two figures. One was slim, the other was sleek; that was the most I could make of my reconnaissance.

The innkeeper appeared in great excitement. ‘Your paper woke them up,’ he said gleefully. ‘The dark fellow went as white as death and cursed like blazes, and the fat one whistled and looked ugly. They paid for their drinks with half-a-sovereign and wouldn’t wait for change.’

‘Now I’ll tell you what I want you to do,’ I said. ‘Get on your bicycle and go off to Newton-Stewart to the Chief Constable. Describe the two men, and say you suspect them of having had something to do with the London murder. You can invent reasons. The two will come back, never fear. Not tonight, for they’ll follow me forty miles along the road, but first thing tomorrow morning. Tell the police to be here bright and early.’

He set off like a docile child, while I worked at Scudder’s notes. When he came back we dined together, and in common decency I had to let him pump me. I gave him a lot of stuff about lion hunts and the Matabele War, thinking all the while what tame businesses these were compared to this I was now engaged in! When he went to bed I sat up and finished Scudder. I smoked in a chair till daylight, for I could not sleep.

About eight next morning I witnessed the arrival of two constables and a sergeant. They put their car in a coach-house under the innkeeper’s instructions, and entered the house. Twenty minutes later I saw from my window a second car come across the plateau from the opposite direction.