ollowed!" she announced in a low tone.
"Don't look around."

"What makes you think so?" Amy inquired skeptically.

"Ever since we left the park a man has been trailing us."

"Are you sure?"

"Every time we stop he does too. I can see his reflection now in the
plate glass. He's pretending to be looking into that jewelry store
window but he's really watching us."

"You mean the man in the gray topcoat?"

"Yes."

"Maybe he's a plain-clothes man who is after me," Amy said uneasily.

"We can soon find out. Come on!"

Catching Amy's arm, Penny steered her into the department store. They
sauntered leisurely through the aisles, frequently pausing to examine
merchandise. Unobtrusively, they kept watch of the main entrance.

"Here he comes, just as I knew he would!" Penny exclaimed in an
undertone as she caught a glimpse of the man entering the store. "We
must shake him quickly now."

They walked swiftly down the aisle and took a crowded elevator to the
top floor.

"Now we'll walk down three flights of stairs," Penny commanded.

Already they had lost sight of the man, but to make certain that he
would not catch them again, they crossed to the opposite side of the
building and took a down-going elevator to the main floor. Mingling
with the crowd they emerged upon the street.

"We certainly gave him the slip," Amy laughed.

"My father taught me that trick. Even a trained detective finds it
difficult to follow a person who is aware he is being shadowed."

"I guess I'll say goodbye to you here," Amy said regretfully. "I hope
I'll see you again soon."

"Yes, indeed. I intend to talk with Mrs. Dillon about that painting
she bought. I'll let you know what she says."

The girls parted company but Penny did not leave the scene. Instead,
she walked across the street, establishing herself in a doorway where
she could keep watch of the department store entrance.

"Two can play at this game of shadowing," she chuckled.

It was nearly twenty minutes before the man who had been following
Penny and Amy emerged from the store. She noted him instantly. He was
a tall, thin man dressed entirely in gray.

"I don't believe I've ever seen him before," Penny thought.

When the man moved off down the street, she crossed the street and
trailed him. He walked swiftly and did not once glance backward,
apparently having no suspicion that he was being followed.

Once the man paused to glance into the window of a paw