“I shall never do that,” I answered; “you have brought detection as near an exact science as it ever will be brought in this world.”

My companion flushed up with pleasure at my words, and the earnest way in which I uttered them. I had already observed that he was as sensitive to flattery on the score of his art as any girl could be of her beauty.

“I’ll tell you one other thing,” he said. “Patent-leathers and Square-toes came in the same cab, and they walked down the pathway together as friendly as possible — arm-in-arm, in all probability. When they got inside, they walked up and down the room — or rather, Patent-leathers stood still while Square-toes walked up and down. I could read all that in the dust; and I could read that as he walked he grew more and more excited. That is shown by the increased length of his strides. He was talking all the while, and working himself up, no doubt, into a fury. Then the tragedy occurred. I’ve told you all I know myself now, for the rest is mere surmise and conjecture. We have a good working basis, however, on which to start. We must hurry up, for I want to go to Halle’s concert to hear Norman Neruda this afternoon.”

This conversation had occurred while our cab had been threading its its way through a long succession of dingy streets and dreary byways. In the dingiest and dreariest of them our driver suddenly came to a stand. “That’s Audley Court in there,” he said, pointing to a narrow slit in the line of dead-coloured brick. “You’ll find me here when you come back.”

Audley Court was not an attractive locality. The narrow passage led us into a quadrangle paved with flags and lined by sordid dwellings. We picked our way among groups of dirty children, and through lines of discoloured linen, until we came to Number 46, the door of which was decorated with a small slip of brass on which the name Rance was engraved. On inquiry we found that the constable was in bed, and we were shown into a little front parlour to await his coming.

He appeared presently, looking a little irritable at being disturbed in his slumbers. “I made my report at the office,” he said.

Holmes took a half-sovereign from his pocket and played with it pensively. “We thought that we should like to hear it all from your own lips,” he said.

“I shall be most happy to tell you anything I can,” the constable answered, with his eyes upon the little golden disc.

“Just let us hear it all in your own way as it occurred.”

Rance sat down on the horsehair sofa, and knitted his brows as though determined not to omit anything in his narrative.

“I’ll tell it ye from the beginning,” he said. “My time is from ten at night to six in the morning. At eleven there was a fight at the White Hart; but bar that all was quiet enough on the beat. At one o’clock it began to rain, and I met Harry Murcher — him who has the Holland Grove beat — and we stood together at the corner of Henrietta Street a-talkin’. Presently — maybe about two or a little after — I thought I would take a look round and see that all was right down the Brixton Road. It was precious dirty and lonely. Not a soul did I meet all the way down, though a cab or two went past me. I was a-strollin’ down, thinkin’ between ourselves how uncommon handy a four of gin hot would be, when suddenly the glint of a light caught my eye in the window of that same house. Now, I knew that them two houses in Lauriston Gardens was empty on account of him that owns them who won’t have the drains seed to, though the very last tenant what lived in one of them died o’ typhoid fever. I was knocked all in a heap, therefore, at seeing a light in the window, and I suspected as something was wrong. When I got to the door —”

‘You’re quite sure it’s all right for you?’

‘Perfectly all right.’

And again they were still. The launch twanged and hooted, somebody was singing. Then as if the night smashed, suddenly there was a great shout, a confusion of shouting, warring on the water, then the horrid noise of paddles reversed and churned violently.

Gerald sat up, and Gudrun looked at him in fear.

‘Somebody in the water,’ he said, angrily, and desperately, looking keenly across the dusk. ‘Can you row up?’

‘Where, to the launch?’ asked Gudrun, in nervous panic.

‘Yes.’

‘You’ll tell me if I don’t steer straight,’ she said, in nervous apprehension.

‘You keep pretty level,’ he said, and the canoe hastened forward.

The shouting and the noise continued, sounding horrid through the dusk, over the surface of the water.

‘Wasn’t this BOUND to happen?’ said Gudrun, with heavy hateful irony. But he hardly heard, and she glanced over her shoulder to see her way. The half–dark waters were sprinkled with lovely bubbles of swaying lights, the launch did not look far off. She was rocking her lights in the early night. Gudrun rowed as hard as she could. But now that it was a serious matter, she seemed uncertain and clumsy in her stroke, it was difficult to paddle swiftly. She glanced at his face. He was looking fixedly into the darkness, very keen and alert and single in himself, instrumental. Her heart sank, she seemed to die a death. ‘Of course,’ she said to herself, ‘nobody will be drowned. Of course they won’t. It would be too extravagant and sensational.’ But her heart was cold, because of his sharp impersonal face. It was as if he belonged naturally to dread and catastrophe, as if he were himself again.

Then there came a child’s voice, a girl’s high, piercing shriek:

‘Di—Di—Di—Di—Oh Di—Oh Di—Oh Di!’

The blood ran cold in Gudrun’s veins.

‘It’s Diana, is it,’ muttered Gerald. ‘The young monkey, she’d have to be up to some of her tricks.’

And he glanced again at the paddle, the boat was not going quickly enough for him. It made Gudrun almost helpless at the rowing, this nervous stress. She kept up with all her might. Still the voices were calling and answering.

‘Where, where? There you are—that’s it. Which? No—No–o–o. Damn it all, here, HERE—’ Boats were hurrying from all directions to the scene, coloured lanterns could be seen waving close to the surface of the lake, reflections swaying after them in uneven haste. The steamer hooted again, for some unknown reason. Gudrun’s boat was travelling quickly, the lanterns were swinging behind Gerald.

And then again came the child’s high, screaming voice, with a note of weeping and impatience in it now:

‘Di—Oh Di—Oh Di—Di—!’