CHAPTER XVIII

The Warning Message Although their flight as stowaways in the airplane was one of the most dangerous and perilous adventures that had ever befallen the Hardy boys, it was at the same time the most monotonous. Back there in the darkness they could see nothing and they could hear very little except the roar of the engine. They were not uncomfortable and they did not suffer from lack of air, but it was not a pleasant sensation to reflect that they were high above the earth, wholly at the mercy of the rascals up in the…