"That's a possibility," Mr. Nichols agreed after a moment of thought.

"From the first his connection with the Imp has been odd to say the least. I'll have a talk with him tomorrow and see what I can learn."

When Penny and her father entered the house, Mrs. Gallup was still searching the lower floor.

"Anything more missing?" the detective asked.

"Not that I can discover. The silver is all here."

"Apparently only the Black Imp was taken," Mr. Nichols said musingly.

"That little figure must guard some important secret."

"I never dreamed it could be valuable," Penny said. "I liked it only because it was a copy of Amy's statue. I thought the work rather crude."

"I doubt that the figure has any intrinsic value," Mr. Nichols answered slowly, "but for some unknown reason, it's highly important to the man who stole it."

That evening Penny accompanied her chum, Susan, to a moving picture show, but although the bill was an exceptionally good one, she found it difficult to center her attention upon the screen. She kept thinking of the Black Imp and wishing that she could recover it or at least solve the mystery of its strange disappearance.

"I'm afraid I'll just have to forget it," she thought gloomily, "but at least I'm making a little headway in tracing the persons who may know something about the stolen Rembrandt."

Penny was convinced that if only she could maintain a patient vigil at the Post Office, in time the ex-museum worker would appear there for his mail. The next morning found her at her usual station, determined not to become discouraged by failure.

For three long hours she kept faithful watch of the General Delivery window. A great many persons came and went but no one who remotely resembled Mr. Hoges. Penny became aware of a growing hunger although it was not yet noon. She noticed a restaurant directly across the street.

"I'll slip over there and have a sandwich," she decided. "It will only take a minute."

The restaurant was crowded. It was impossible for Penny to find a table near the window. She was forced to sit at the rear of the room and other diners blocked her view of the street.

She hastily ate her sandwich and returned to the post office. Scarcely had she taken her position near the door, when the clerk at the General Delivery window signalled her.

"Weren't you the girl who wanted to see George Hoges?"

"Yes, I am."

"He just called for his mail a few minutes ago."

Penny's heart sank. After waiting nearly two days she had missed the man. And it was entirely her own fault.

"You didn't see which direction he went?"

"No, I didn't," the clerk answered. "But he left only a minute or so before you came in."

"Then maybe I can still catch him," Penny said hopefully.

She ran from the building, pausing on the outside steps to survey the street. A man who from a distance resembled the ex-museum worker was just turning the corner.

"I believe it's Mr. Hoges!" she thought excitedly.

Penny raced to the corner. The man was only a little ways ahead, and as he paused for an instant to glance into a shop window, she caught a glimpse of his face. It was George Hoges.

Penny's original intention had been to question the man, but now she slightly altered her plan. She would follow him.

The ex-museum worker walked rapidly down the street with Penny in close pursuit. However, she took care not to draw too near, fearing that he might glance back and recognize her.

At first Hoges kept to the main streets, but presently he turned toward a section which was somewhat deserted. Penny was forced to drop farther behind. They came soon to a factory district with many vacant buildings, similar in many respects to the Franklyn Street section.

Hoges halted in front of an old building, and disappeared inside. When Penny drew near a minute later, he was nowhere to be seen.

The office directory was of no use, for not a single listed name was familiar to the girl. However, Penny had a suspicion that the man she sought might have engaged the top floor of the building. She was thinking of mounting the stairs when the janitor appeared.

"Looking for someone?" he inquired.

"Yes, but I don't know his name," Penny replied. "He is an artist I think."

"The top floor is rented to a firm of commercial artists," the man informed.

"That must be the place I'm looking for. Thank you."

Penny slowly mounted four long flights of stairs, pausing at the top landing to regain her breath.

She observed with keen interest that several doors opened off the hallway and each bore a freshly lettered sign:

"Private--Keep Out."

Penny glanced down the stairs to make certain that the janitor had not followed her. Then she tiptoed along the hall, pausing by the first door to listen. She could hear an indistinct murmur of voices. Now and then she caught a few words.

"The girl sent it back," she overheard. And then, a moment later: "We'll have to find someone to do her work. She may take it into her silly head to squeal too."

Could the men be speaking of Amy Coulter? Penny felt sure that the letter Hoges had received at General Delivery had come from her.

A loud creaking sound from the direction of the stairway caused Penny to straighten up and listen intently. Someone was coming! While it might be only the janitor she did not wish to be seen. Frantically, she glanced about for a hiding place.

At the end of the hall a broom closet stood with door slightly ajar.

She darted to it and shut herself inside, leaving a wide crack through which she could look out.

The corridor was dark. At first she could not see the newcomer very plainly. She distinguished only a tall, shadowy form.

However, as he paused at the very door where Penny had stood listening only a moment before, she caught an excellent glimpse of his face. She saw then, with a start of recognition, that it was Hanley Cron.

CHAPTER XVIII

Captured

The art critic rapped three times on the door. It opened instantly and closed after him as he vanished inside.

After waiting a few minutes, Penny tiptoed back down the hall. Her suspicions had been aroused and she was determined to learn what was going on inside the room.