Ted Wilford, who writes for the semi-weekly Town Crier during college vacations, and his friend Nelson Morgan, who is a part-time photographer for the same paper, find themselves aboard a Great Lakes ore carrier in this fourteenth book of the popular Ted Wilford series. Small operational accidents on the Shamrock are causing delays that threaten a vital contract, and the two young men are sent to investigate. Events take a more serious turn when John Star, a wiper in the engine room, disappears. Was he drowned trying to swim ashore, or is he hiding somewhere on the ship? A general search reveals no one; but Ted and Nelson, working as members of the crew, encounter perplexing circumstances. Had the radio operator conveyed a false message to change course? Why did the mate decide not to report a passing ship? And, who was responsible for the outbreak of petty thievery aboard the Shamrock? Most mysterious of all, what was the identity of the small boat named Gray Lady, that appeared at strange times and was called a phantom boat by the sailors? Ted and Nelson's efforts to unravel the mystery, combined with the realistic background of Great Lakes shipping, make this a first-rate Ted Wilford mystery.