However, as Joe had said, the car had served its purpose. The boys had picked it up cheaply, with a definite object in view. As told in the preceding volume of this series, "The Hardy Boys: The Shore Road Mystery," there had been a series of mysterious automobile thefts on the Shore Road leading out of Bayport, numerous pleasure cars and trucks having been stolen, and no amount of investigation on the part of the police had succeeded in revealing their whereabouts or the identity of the thieves. Frank and Joe Hardy, who had earned considerable local fame by their activities as amateur detectives, in emulation of their famous father, had decided to lay a trap for the automobile thieves and, buying the gorgeous rattle-trap, parked it on the Shore Road for several nights, concealing themselves in the rear. After many adventures, the Hardy boys captured the thieves and recovered the stolen cars. They collected several handsome rewards for their work, so their investment in the roadster proved exceedingly profitable after all. "The car owners around Bayport have sure been breathing easier since that affair was cleared up," said Biff. "I don't think there'll be any more car thieving for a long time," Tony declared. "The two sleuths here put a stop to that." "We had a good time doing it," Frank admitted. "I'm rather sorry it's all over." "Never satisfied!" commented Biff. He prodded the wheel with his foot and the _Envoy_ swung about with its nose pointing down the bay. Barmet Bay, three miles long, opened on the Atlantic, and in the distance the boys could see a motor yacht that ran daily between Bayport and one of the towns on the coast, a trim little passenger craft that was proceeding toward them at a fast clip. "Where are you going?" shouted Tony. "Out to meet the passenger boat." "Race you!" "So will we!" called Frank. Biff abandoned his indolent posture and settled down to take advantage of his head start. His boat leaped ahead with a roar. Tony Prito had to make a half turn before he could get under way. The Hardy boys were similarly unprepared, but they had no doubt of the ability of the _Sleuth_ to overhaul Biff's boat quickly. Their craft was one of the speediest in the bay, with smooth lines and a powerful engine. They had trouble on the turn, for the swells of the other boats caught the _Sleuth_ and put it off its course, and by the time the craft was nosing in pursuit, Biff Hooper had a good lead and Tony Prito was also ahead of them. "Step on it!" said Joe. Frank "stepped on it," and the _Sleuth_ began eating up the intervening distance. Rocking and swaying, prow well out of the water, the boat overhauled the _Napoli_ and Frank grinned at Tony as they crept by. The Italian lad was getting every ounce of speed of which his engine was capable and although he jockeyed to try to put the Hardy boys off the course, they sped on and soon left him behind.