There was no mention of the bomb episode on the railroad bridge the night before, however. Bob knew that the authorities would not permit the publication of any such items if they could prevent it so he was not surprised. Presently the rest of the family appeared and they went in to breakfast.
Mr. Cook's mail was lying on the table by his plate; it was his custom every morning to glance it over while he was eating. While Mrs. Cook talked to Bob about Harold, her husband looked through his letters. Suddenly he uttered an exclamation of surprise. "Here's a queer thing," he said.
"What?" demanded Mrs. Cook anxiously. She had been very nervous lately.
"This postcard," said Mr. Cook. "Listen to what it says. 'Take the advice of one who knows and keep your automobile home at night.'"
Bob turned pale. "What does it mean!" inquired Mrs. Cook.
"I'm sure I don't know," said her husband.
"How is it signed?"
"It is not signed at all."
"I can't imagine what it's all about," said Mr. Cook. "As far as I know, our car hasn't been out of the garage at night for over a week."
"Perhaps Heinrich has had it out," Mrs. Cook suggested.