"Go back! Go back!" he cried in a strained, harsh voice. "Back to the apartment!"
As he turned around in the street, Greg stole a glance into the back of the cab. He could not see the face of either man, but revealed by the light of a street lamp he saw the little black book open in de Socotra's hands. So the worst had happened. Saunders had betrayed them, and de Socotra had discovered the substitution. Greg's heart contracted sharply. How could he warn Amy in time?
He turned back into Amsterdam Avenue, and headed north again. In his efforts to collect his thoughts he instinctively slowed down. De Socotra hammered on the glass and yelled:
"Faster! Faster! What's the matter with you?"
Presently he changed his mind. Opening the door again he said: "Stop at that drug-store yonder, I want to telephone."
The two men tumbled out of the cab. They were disputing excitedly in Spanish. Saunders seemed to be making some kind of appeal, which de Socotra furiously denied. The latter's face was livid and distorted with rage. Gone was the smiling courteous veneer. Greg was appalled at the revelation of the man's true character. On the other hand Saunders seemed almost ready to weep.
"He is scared now at what he started," thought Greg grimly.
De Socotra, waving Saunders away, went into the drug-store. Saunders, holding his hands above his head and talking to himself, walked blindly away down the side street.
"He hasn't even got wit enough to warn her what is coming," thought Greg. "I must do it."
Through the lighted windows of the drug-store Greg saw that the telephone booth that de Socotra entered adjoined the soda-water counter. Obeying a sudden impulse he followed him into the store.