"I do," Mrs. Dillon maintained loyally, "but I did not depend entirely upon his opinion. I am a very good judge of pictures myself."
"Has it occurred to you that possibly you did not receive the same painting which you purchased? I understand that sometimes art thieves prey upon innocent buyers by showing them a genuine picture and then delivering into their hands only a cheap copy."
"I am too shrewd to be so easily duped," Mrs. Dillon retorted. "I don't mind telling you that I protected myself against just such trickery."
"How?"
"When I viewed the picture and satisfied myself as to its quality, I marked the back of the canvas with a tiny symbol. In that way you see, another painting could not be substituted, for the marking would be absent."
"The symbol might be duplicated."
"No, I would instantly detect the difference."
Penny sat lost in thought for a moment. She now understood the significance of the strange marking on the back of the Rembrandt which had puzzled Amy and herself. Was it possible that the Coulter girl had been mistaken in the quality of the painting?
"Mrs. Dillon," she said after a long silence, "you confidently believe that your painting is the same one which was stolen from the Gage Galleries?"
"All I know is that my picture is a genuine Rembrandt. I did not learn that a picture had been stolen from the museum until after I had made my purchase. I do not know even now that I have this same painting."