In the meantime, the young inventor realized he had an awesome responsibility. He must not only make the best use of the brain energy during its stay on earth, but also keep it from falling into the hands of treacherous Brungarian plotters. Tom's thoughts were suddenly interrupted by the sound of girls' voices. Sandy and Phyl were standing in the doorway of the space-communications laboratory. "Talk about deep thinkers!" Sandy said teasingly. "Goodness, we had no idea we'd be interrupting a session of the brain trust," Phyl added with a mischievous sparkle in her brown eyes. "Maybe we should go away again, Sandy!" "Hey! Hold it, you two!" Bud exclaimed. "What do you think, Tom--are these the visitors we've been expecting from outer space?" "Well! I like that!" Sandy pouted. "Do we look like a couple of little green people?" Tom chuckled and seized the opportunity to do a little teasing of his own. "I think it's just your pointed heads that fooled us, Sis." Then, as the two girls broke down in laughter, he added, "Why the unexpected visit?" Sandy and Phyl explained that they had come to invite the boys to a picnic cruise on Lake Carlopa the next day. "And while we're here, since it's practically quitting time anyhow," Sandy went on, her blue eyes twinkling, "we might even let you drive us some place for dinner." "Guess they've trapped us, Bud," Tom said with a grin. "Okay, it's a deal. But first we have something to show you." He took the girls to his laboratory to show them the robot creature. "It's marvelous!" Sandy exclaimed, and Phyl agreed. Early the next morning Bud called for Tom and Sandy in his tomato-red convertible. Then they stopped at the Newtons' house to pick up Phyl. Each girl had packed a picnic basket for the day's sail. "Hmm. Looks as though we're going to be well fed," Bud commented jokingly. "What's on the menu, girls?" "Chicken and ham sandwiches..." Sandy began. "Pickles, olives, hard-boiled eggs, potato salad..." Phyl went on. "Chocolate cake, milk..." Sandy took up the list. "Stop! You have us hungry as bears already!" Tom warned. "Right!" Bud agreed. "Come on! Let's get this cruise under way!" The two couples drove to the Shopton Yacht Club dock on Lake Carlopa. There they boarded the _Sunspot_, a beautiful thirty-foot sailing ketch with auxiliary engine which Mr. Swift and Mr. Newton had purchased for a frequently promised but not yet realized joint family vacation. The craft was equipped with twin gravitex stabilizers, mounted one on each side of the hull. These gave it amazing smoothness even when plowing through rough seas. They were adaptations of a device Tom had invented for his space kite and _Cosmic Sailer_. "Oh, what a gorgeous day for a sail!" Phyl said, aglow with enthusiasm. The sky was a cloudless blue. Under a hot summer sun, a brisk breeze was ruffling the lake into tiny whitecaps. The two couples cast off eagerly and were soon scudding out across the water under full sail.