It was still as a tomb.

He could hear his own heart beat and he could also hear the heavy breathing of the other man.

"Sounds like he had been running and was just catching his breath," was Billie's mental comment.

After some minutes the man's breathing became more quiet and Billie heard him slowly descending the stairs.

"This won't do," thought Billie. "He probably has some kind of a light, and if he gets on the landing and I'm up here, I'll be like a man up a tree."

The lad sat down and slowly slid toward the bottom.

Being only a few steps from the landing, Billie was down first.

He crowded to the right and listened.

The other was now nearly on the landing. Now he was on the landing, hugging the wall on the side opposite Billie. Now they pa.s.sed each other, or rather the man pa.s.sed Billie, for Billie stood perfectly still.

It seemed as though he must hear Billie's breathing, but if he heard anything he must have thought it his own echo, never dreaming that he was not alone in the pa.s.sage.

Now Billie could hear him ascending the stairs leading to Santiago's house, and his hope rose high.

"He must know how to open the floor," thought Billie. "I'll be right there when he does."

Silently as a cat Billie crept up the stairs behind his unknown companion.

Near the top the man stopped and a minute later he flashed an electric light against the stone overhead. Another minute and he heaved with the top of his head and the slab slid back.

"And now," exclaimed Billie in a deep voice, "put your hands over your head!"

Whether from fear or from the unparalleled surprise caused by hearing a human voice at such a time and in such a place, instead of obeying Billie's command, Strong's hands--for Strong it was--fell limp at his side and his electric torch fell to the stones beneath his feet.

"All right," continued Billy, "if that's the way you feel about it; but just remember that a single false move and I'll cut this automatic loose among your ribs. Now climb out a step at a time."

With face as white as marble at the shock he had just sustained, Strong obeyed implicitly and Billie was soon standing on the stone patio, looking Strong in the face.

"You're a good one, you are," he said sarcastically. "I should think you'd be ashamed to call yourself an American."

"What do you mean?" asked Strong in a trembling voice.

"Why, first of all, stealing from the bank, and then selling your own countrymen to the Mexicans."

"Who have I sold?"

"Do you mean to say that you didn't sell Gen. Funston to the greasers for ten thousand dollars?"

"Of course I do!" in a somewhat stronger voice.

"Perhaps you'll deny that you are Strong, the mountebank. You don't think for one minute that I don't know you in spite of your make-up, do you?"

"No, I'll admit that I'm the mountebank. As for my name that is of small importance in a country like this. But I did not sell Gen. Funston, as you put it. I knew the man I pointed out was not Funston and I knew that as soon as the Mexicans found it out they would let him go. Some one might have told them rightly. As it was I spoiled their game and I got the money. Do you think it any crime to do that?"

"That's a matter I am not in a position to discuss," was Billie's answer. "But how about robbing the bank?"

"I had as much right to the box as any one."

"You'll have to prove that to some one besides me; all I can do is to turn you over to the authorities."

"Never!" cried Strong. "I'll die before I'll rot in a Mexican jail!"

He uttered a peculiar noise and before Billie could imagine what it meant, he felt himself seized from behind by a pair of hairy hands.

He had been in that clutch once before and recognized in an instant that he was in the grip of the ape.

He gave one loud cry for help and then turned loose with his automatic.

The tumult which followed is beyond description. Billie's shout was as nothing compared to the cry of the ape as one of the bullets struck him in the leg and another pierced his foot.

Loosing his hold upon the lad, he grabbed for the weapon, but Billie managed to evade him and would undoubtedly have slain the animal had not Strong sprung to his a.s.sistance, with the result that in another minute Billie was disarmed.

Ill would the lad have fared then, at the hands of his two a.s.sailants, had not the noise attracted to the scene several soldiers, while an instant later came a loud shout as Donald and Adrian dashed into the patio.

On the other side of the square they had heard Billie's shout, followed by the automatic, and had rushed to his aid.

In another minute both Strong and his hairy friend were overcome and securely bound.

"Where did you find him?" asked Donald, pointing to Strong.

"Down there," was Billie's reply, as he pointed toward the still open underground pa.s.sage way.

"How did he get there?"

"I suppose he entered from a similar entrance in Don Esteban's patio. I have had an idea all the time that there was some reason for the position of these two houses."

"But it doesn't lead into the bank. How could he steal the box out of the vault?"

"There is the real thief!" exclaimed Billie, pointing to the ape.

"He sneaked in while Strong kept the bank employes engaged. By some mistake in his understanding he put the envelope back in the bank the next day instead of putting back the box. It was he who crawled through the bars into Santiago's library. He was also the devil who scared the maid almost into fits."

"Well! Well!" exclaimed a voice from the gateway. "I never could have believed it."

The voice was that of Don Esteban, who had entered while Billie was speaking.

"I have come to see this strange man, Santiago Ojeda," he explained. "What says the doctor?"

"Here comes the doctor now," announced Adrian as the physician made his appearance in the gateway. "He can speak for himself."

CHAPTER x.x.xI.