It was sundown when the Double O and the Box B riders finished the task of getting the cattle back on their own ranges. They stopped at the boundary between the ranches and the Double O cattle plodded northward onto their own range.

“How many cattle you figure you’ve lost?” Joe asked the owner of the Double O.

“Right around 350,” replied Nels. “How many have you?”

“It’s more than that. A good 500 head and maybe a few more have been stolen in the last few months. I tell you, it’s hit us mighty hard.”

Nel’s pale eyes hardened and his huge hands moved convulsively for he was a man of deep emotion.

“We shall stop that, and soon,” he roared. “Tomorrow we go see Cook and line him up. After that we’ll clean out Dirty Water and maybe that will stop the rustling.”

Joe looked thoughtful.

“I don’t think we’ll be able to swing Cook along with us,” he said, “and when it comes to cleaning up Dirty Water, we’ll have to have some proof.”

“I’m tired of waiting,” said Nels. “Action I got to have. There’s no law in the valley unless we make it ourselves.”

“You’re right,” agreed Slim, “but let’s wait until we’re sure of the gang responsible for this rustling.”

Nels grumblingly agreed that Slim’s advice was logical and they parted with the agreement that the Box B foreman would ride over to the Double O in the morning and that Nels would accompany him on a visit to the Cook ranch.

“What sort of a fellow is this Cook?”

“All bad,” replied Joe. “He runs the Diamond Dot, a small outfit that lies east of the Double O and the Box B and north of Dirty Water. His range backs right up against the Cajons. We’ve had lots of trouble with him over our water rights.”

“Has he been losing cattle the last year?”

“Claims he’s lost a bunch, but I wouldn’t take his word for anything. Unless we keep a close watch, he runs his cattle over on our range and they clean up some of our best grazing land.”

“Then it won’t be much use to see him tomorrow?”

“I don’t think so, but it will satisfy Nels, and if Cook has really been losing beef he may throw in with us. He has a lot of riders and they’re all tough birds. If the three outfits made a united stand, we’d sweep this valley clean of every undesirable hombre that’s come in here the last couple of years.”

When they reached the home place, Joe went at once to report the events of the day to the owner of the Box B while the cowboys hurried into the cookhouse, where Lee Wu had supper ready.

“Golly, but I thought there was going to be trouble when Joe called Nels Anderson a rustler,” said Walt Kelly, between mouthfuls of bread.

“There would have been if Al Bass hadn’t grabbed his hand,” put in jovial Pat Beals. “I’m telling you, my hair was standing on end.”

“We’re finally getting started on the right track,” said Walt, “even if it almost took bloodshed to get these outfits together. Believe me, it’s going to be tough for the rustlers from now on.”

Slim had been watching Doug Huston and he thought he saw the cowboy’s face twitch slightly. One thing, Doug had expressed no elation at the peacemaking with the Double O.

There was only the faintest tinge of light over the Three Soldiers as they left the cookhouse. Up at the ranch house, a light glowed in Adam Marks’ bedroom and Slim knew that the foreman was recounting in great detail the happenings of the day.

Slim walked down to the corral and whistled softly. Out of the shadows came Lightning, and Slim climbed up to the top rail and ran his hands through the sorrel’s thick mane.

“We made a little progress today,” he said softly and Lightning tossed her head in agreement. “But we’ve got a long way to go,” added Slim, and again the sorrel nodded.

Chuck came down from the bunkhouse and climbed atop the corral.

“Doing a little heavy thinking?” he asked.

“Trying to, but the results are about zero.”

“I’d like to know how the 800 and some head that have been stolen from the Box B and the Double O were taken out of the valley,” said Chuck.

“When we discover how that’s been done, we’ll be just about at the end of this mystery.”

“They’ve been rustled in small lots, but even then cattle can’t fly.”

“That’s one reason I’m anxious to see what kind of a place the Diamond Dot runs. Joe Haines don’t like that outfit a bit.”

“He didn’t like the Double O until he realized that somebody was trying to get the two outfits to fighting,” pointed out Chuck.

“There won’t be any more trouble along that line and I feel we’ve made a little progress, but not enough.”

Slim’s fingers, exploring an inside pocket, came in contact with the cartridge he had found at the scene of Adam Marks’ ambush. He had two definite clues, the exploded shell and the V-shaped hoofprint. Somewhere in the valley he must find the rider of that horse.

The cowboy detectives returned to the bunkhouse. The foreman was still at the ranch house and the other Box B riders were engaged in various personal tasks.

Slim and Chuck rolled in early, and a few minutes later the others were in their blankets.

Slim fell into a restless sleep, for even after his body relaxed his mind was working on the rustling mystery. Thus it was that he heard a slight noise down at the corral and awakened almost instantly.

Slim pulled on his trousers, picked up his boots, and left the bunkhouse silently. Someone was in the corral saddling a horse. Slim moved swiftly forward. The moon, which had topped the Cajons, was shrouded with clouds.

The cowboy detective paused beside the main gate of the corral to see what was going on inside and had just stuck his head above the top rail when a rope swished out of the shadows and settled over his head. Before he could utter a sound, it was jerked tight and he fell sprawling to the ground, gasping for breath.

Slim clawed at the rope, but it was too tight. Someone was running toward him, coming out of the corral.

The moonlight brightened for an instant and Slim looked up into a masked face.

“Smart guy,” came a hard, chilling voice. “Well, you’re not as smart as you think you are.”

Slim tried to dodge, but the other man struck him with a short, heavy club, and the cowboy detective lost consciousness. When he finally opened his eyes, the moon was well toward its zenith and his head throbbed dismally.

He tried to move, but found his arms and feet securely bound and a tight gag in his aching mouth. He managed to roll over and lift his head. He had been carried a hundred yards from the corral and deposited beside the creek. Slim tried to wriggle along the ground, but he made little progress and it was an exhausting effort. He rolled over on his back and looked up at the moon. There was nothing to do but wait for morning.

It was well after midnight when Slim heard a horse approaching the Box B. It was coming slowly as though the rider was afraid of discovery. Then the gate of the corral was opened and Slim knew that his assailant had returned. There was no question now but that one of the Box B riders was allied with the rustlers for Slim felt sure that the unknown rider had slipped away to inform the other members of the gang that the Box B and the Double O were standing shoulder to shoulder to resist any further depredations.

The aching hours went by slowly. The moon dropped behind the Three Soldiers and for over an hour the Creeping Shadows country was cloaked in the deepest night. Then the peaks of the Cajons were touched with the first streaks of another day and Slim moved a little to rest his tortured body.

It was an hour later before he was found and then Chuck saw him lying beside the creek and hurried to slash his bonds.

Slim had to be helped to a sitting position, for the circulation had long since stopped in his feet and hands. Chuck worked carefully, rubbing the bruised members. Slim cried out in pain once or twice as the blood again coursed through the arteries and veins. His tongue was badly swollen and Chuck ran for a cup of water. Returning, he took a clean handkerchief and soaked it with water. This Slim placed in his mouth, sucking gratefully at the cool liquid.

Joe Haines heard that something was wrong and came hurrying down, the other Box B riders following him. Slim waved aside their questions for his jaws ached too much to talk and it was not until he had downed a bowl of breakfast food that he told them the full story.

“Have any idea who it was?” asked Joe.

“Not the slightest,” replied Slim, deciding not to reveal that he had heard the rider return to the Box B.

Walt Kelly hurried down to the corral to look at the horses.

“Every cayuse is there,” he said when he returned.

“Then I can’t figure out what anyone was doing in our corral,” said Joe.

“Maybe he was going to run off with the horses and Slim came along just in time to give him a scare,” suggested Doug.

“Well, maybe,” agreed Joe, but it was plain that such an explanation did not satisfy him.

When they left the cookhouse, Joe turned to Slim.

“Feel like riding over to the Double O with me?”

“I’ll be all right in a few minutes. Count me in. I want to be along when you talk with the boss of the Diamond Dot.”

Slim went to the bunkhouse while the others hastened down to the corral to get their mounts. The cowboy detective was firmly convinced that someone in the bunkhouse had slugged him the night before and left him hog-tied along the creek.

With quick, deft hands he searched one bunk after another. It was not until he reached Doug Huston’s duffel bag that he found anything. Wadded in the bottom was a black cloth which might easily be tied around the lower part of the face to form a mask. Slim nodded grimly. His suspicions that Doug was the rustlers’ key man on the ranch were rapidly being confirmed.

Slim rammed the black cloth back into the duffel bag and slipped on his chaps, slung his gun belt around his hips, and started for the corral.

An excited group was gathered at the gate, looking at tracks which led into the corral.

“Look here, Slim,” cried Chuck. “One of the rustlers, the guy that took a shot at the boss, rode right into our own corral last night. Here’s his tracks going in, but there’s none coming out.”

Slim looked down at the hoofprint to which Chuck pointed. There was the telltale V-shaped mark.