Billie and Mr. Black heard them coming.
"Go to the roof," commanded Mr. Black, speaking to the two females, "and keep yourselves and the little girl out of sight. We will hold them back here as long as we can and then we will also come to the roof."
The command had hardly been obeyed than the Mexicans began to crowd up the stairs. They were met with shot after shot, but at last all the weapons were empty.
"Run for the roof," said Mr. Black as he arose to his feet and with his heavy boot kicked a head which was just coming up the stairs.
Billie obeyed and a minute later the fugitives had gathered upon the last place of safety left.
"If we only had some ammunition," moaned Billie. "Can't we do something?"
Then, as in answer to his own query, he picked up a twelve-pound cannon ball that lay on the roof and, raising it above his head with both hands, hurled it through the opening upon those below.
This unexpected attack caused the besiegers to draw back, but only for a moment. Then they came on again. In his desperation, Mr. Black, with almost superhuman strength, picked up the cannon itself, just as Billie had picked up the ball, and hurled it down the stairs.
Half a dozen men fell beneath its weight, while the others, frightened at such an exhibition of strength, fell back in dismay.
A shout from the captain urged them forward, but ere they could gather their courage for another rush there came the sound of a volley in the patio below and a minute later Adrian rushed up the stairs, followed by Captain Lopez and a squad of his soldiers.