He came forward as the person first named entered the shop.
"How can I serve you, sir?" he inquired in a respectful voice.
The person addressed drew from his pocket a piece of paper on which a name was inscribed.
"I want that," he said; "do you happen to have it?"
The shopman's face was tinged with a slight color as he read the name inscribed on the paper.
"You are aware, I suppose, that this is a subtle poison?" he said, interrogatively.
"Yes," said the other, in a tone of outward composure, "so I understand from the friend who desired me to procure it for him. Have you it, or shall I have to go elsewhere?"
"Yes; we happen to have it by the merest chance, although it is rather a rare drug in the materia medica. I will get it for you at once."
The customer's face assumed an air of satisfaction as the clerk spoke, and he sat down on a stool in front of the counter.
James Cromwell quickly placed a small parcel in his hands, and the customer, drawing out a pocketbook, which appeared to be well-filled, paid for his purchase.
He then walked out of the shop, and to the corner of the street, where he waited for an uptown car. As he left the shop, a ragged boy of ten, with a sharp, weazened face entered.
"Wait a minute; do you want to earn a quarter?" demanded the shopman, abruptly.
"Then you must follow the gentleman who just went out of the shop: find out where he lives, and what his name is. Come out, and I will point him out to you."
Just outside of the door, James Cromwell cast his eyes up the street and saw his late customer in the act of jumping on board a Fourth Avenue car.
"There he is," he said, hastily pointing him out to the boy. "You will have to ride, too. Can you catch that car?"
The boy ran forward, and succeeded in overtaking the car and clambering on board.
"Look here, young chap," said the conductor, suspiciously, "have you got any money to pay your fare?"
"Yes, I have," said the boy. "Don't you be afraid, old hoss."
The boy produced the quarter which had just been given him.
"You're richer than I supposed," said the conductor. "Here's your change."
The boy put back the twenty-two cents remaining in the pocket of his ragged pants, and began to look about him for the passenger whom he was required to track. The latter was seated on the left hand side, four seats from the door.