“Then you think that he had nothing to do with it,” he said.

“I wouldn’t go as far as to say that,” answered Shelley. “But I should be prepared to take a bet of ten to one that he knows nothing about the murders.”

“H’m.” Henry did not seem at all impressed, but did not feel inclined to dispute the issue. And, in any case, further argument was prevented by a sudden discovery of Shelley.

“Stop!” he shouted, and, with a shriek of protest from the brakes, the obedient driver brought the speeding car to a sudden standstill.

“What’s the matter?” asked Cunningham in puzzled tones; and Shelley pointed to a stationary car which was just in front of them. It was a fast-looking, rakish sports saloon.

“What price Mr. Wallace?” Shelley murmured, and Cunningham, not for the first time in his career, marvelled at his chief’s wonderful powers of observation, able to pay attention to every vehicle on the road at the same time as he was carrying on a conversation which would have occupied the whole mind of most people.

“Looks like it, doesn’t it?” he said; and then followed Shelley on to the road and over to the empty car.

They looked at the tyres, and then Shelley gave vent to a grunt of pleased satisfaction.

“See,” he said, and pointed to the back off wheel. Cunningham obediently looked, and at once saw the cause of Shelley’s satisfaction. The tyre was a Dunlop, and it had a patch. This was certainly the car that had driven out of Blackthorn Farm, just prior to their arrival at the deserted house!

“Cunningham,” said Shelley, emotion making his voice tremble. “Cunningham, my lad, we’ve got him!”

“Why did he abandon the car, I wonder?” Cunningham murmured.

“Breakdown, I expect,” answered Shelley, as he strode to the front of the car, threw open the bonnet, and made a cursory examination of the engine.

“Well, that was a bit of luck for us, anyhow,” he said, pointing to the petrol-tank, from which he had just removed the cap.

“Ran out of petrol, eh?” said Cunningham, and roared with laughter.

“That’s about it,” answered Shelley. “And not so long ago, either,” he added, feeling the radiator with his hand. “The radiator is still distinctly warm to the touch.”

They hurriedly clambered back into the car, and were soon buzzing along the road again. By this time they had got well up into the hills, and the road twisted and turned almost like a corkscrew. Not far ahead they could see, in a dip of the hills, a stretch of grey mirror—one of the mighty reservoirs which keeps Sheffield supplied with water.

“Should catch him very soon,” Shelley remarked. “He can’t have got more than a mile or so.” He leaned over the front seat in his excitement, as he gave further instructions to the driver.