"The Wailing Siren Mystery" is volume 30 in The Hardy Boys mystery stories. Written by Franklin W. Dixon. Published by Grosset & Dunlap, copyright 1968.

"Caught in their motorboat, the Sleuth, by a sudden storm at sea, Frank and Joe Hardy are helpless when the engine conks out. Drifting farther from shore amid the tumultuous waves, the boys are relieved to see the lights of a yacht. But their SOS is ignored.
The shrill sound of a siren fills the night air. Moments later, a helicopter drops an object alongside the Sleuth. To the young detectives' astonishment it proves to be a wallet containing two thousand dollars. The next day Chet Morton's farm truck, carrying a shipment of high-powered rifles belonging to his uncle, a big-game hunter, has been stolen. These two apparently unconnected events are clues in a tangle of mystery which turns out to be one of the detective brothers' most exciting adventures."

177 page hard cover book in good condition with no rips, tears, or writing.