Marcus swore wrathfully.

“He acted that way once before,” explained McTeague, his hands still in the air.  “He ate some loco-weed back in the hills before I started.”

For a moment Marcus hesitated.  While he was catching the mule McTeague might get away.  But where to, in heaven’s name?  A rat could not hide on the surface of that glistening alkali, and besides, all McTeague’s store of provisions and his priceless supply of water were on the mule.  Marcus ran after the mule, revolver in hand, shouting and cursing.  But the mule would not be caught.  He acted as if possessed, squealing, lashing out, and galloping in wide circles, his head high in the air.

“Come on,” shouted Marcus, furious, turning back to McTeague.  “Come on, help me catch him.  We got to catch him.  All the water we got is on the saddle.”

McTeague came up.

“He’s eatun some loco-weed,” he repeated.  “He went kinda crazy once before.”

“If he should take it into his head to bolt and keep on running——­”

Marcus did not finish.  A sudden great fear seemed to widen around and inclose the two men.  Once their water gone, the end would not be long.

“We can catch him all right,” said the dentist.  “I caught him once before.”

“Oh, I guess we can catch him,” answered Marcus, reassuringly.

Already the sense of enmity between the two had weakened in the face of a common peril.  Marcus let down the hammer of his revolver and slid it back into the holster.

The mule was trotting on ahead, snorting and throwing up great clouds of alkali dust.  At every step the canvas sack jingled, and McTeague’s bird cage, still wrapped in the flour-bags, bumped against the saddlepads.  By and by the mule stopped, blowing out his nostrils excitedly.

“He’s clean crazy,” fumed Marcus, panting and swearing.

“We ought to come up on him quiet,” observed McTeague.

“I’ll try and sneak up,” said Marcus; “two of us would scare him again.  You stay here.”

Marcus went forward a step at a time.  He was almost within arm’s length of the bridle when the mule shied from him abruptly and galloped away.

Marcus danced with rage, shaking his fists, and swearing horribly.  Some hundred yards away the mule paused and began blowing and snuffing in the alkali as though in search of feed.  Then, for no reason, he shied again, and started off on a jog trot toward the east.

“We’ve got to follow him,” exclaimed Marcus as McTeague came up.  “There’s no water within seventy miles of here.”

Then began an interminable pursuit.  Mile after mile, under the terrible heat of the desert sun, the two men followed the mule, racked with a thirst that grew fiercer every hour.  A dozen times they could almost touch the canteen of water, and as often the distraught animal shied away and fled before them.  At length Marcus cried: