f the canvas," Amy suggested.
"Sometimes that will give a clue as to the age of a painting."

They pulled the picture out from the wall and peered behind it.
Directly in the center of the canvas was a strange, complicated symbol
and beneath it the initials, "G. D." Both had been inscribed in India
ink.

"What's that for?" Penny questioned.

"I wonder myself," Amy replied.

"Then it isn't customary to put symbols or initials on the back of a
painting?"

"Decidedly not."

The girls studied the marking for a minute. They could make nothing of
it.

"I can't explain the symbol," Amy said, "but I'm convinced this
painting is a fraud."

Penny had expected such a verdict as it confirmed her own observations,
but for her friend's sake she was sorry that the painting had not
turned out to be the original Rembrandt. Had they actually located the
stolen picture it would be a simple matter to lay their evidence before
the police and demand that Mrs. Dillon be forced to reveal the dealer
from whom she purchased the property.

"Everything is in a queer muddle now," Penny commented thoughtfully.
"Mrs. Dillon really isn't guilty of any crime at all, for she didn't
buy a stolen picture. We can't very well cause her arrest."

"Mrs. Dillon should complain to the police that she was cheated."

"She doesn't know it yet," Penny chuckled. "When she finds out about
it, I imagine she'll never report the dealer. Her own part in the
affair would be too humiliating. Even if she didn't buy stolen
property, that was her intention."

"I suppose the real crooks counted upon just such a reaction," Amy
said. "When they sold her that fake painting they knew they were safe."

"And in the meantime the genuine Rembrandt is still missing," Penny
replied musingly. "I have a suspicion this dishonest dealer, who sold
Mrs. Dillon the fake picture, might be able to throw a little light
upon the subject."

"But how will we ever trace him unless we notify the police?"

"I am afraid that would be a sure way of losing his trail completely,"
Penny replied. "Mrs. Dillon's arrest would be the signal for the
dishonest dealer to get out of town."

"That's probably true."

"We must work this thing out cautiously," Penny declared. "Perhaps if
we went to Mrs. Dillon and talked with her--"

She broke off as they heard approaching footsteps in the hall.

"The maid!" Amy whispered.

"Quick!" Penny exclaimed in an undertone. "Help me get thi