Keith Stewart was one of those pudgy little men nobody thought about much. He had his little workshop in his basement, wrote articles for "Miniature Mechanic", and his wife worked in a shop to make ends meet. He's just barely getting by, but he's doing what he wants to do.
His sister and wealthy brother-in-law plan to sail from England, through the Panama Canal, off to Tahiti, and eventually back and north to Vancouver, where they intend to relocate. At his brother-in-law's request, Keith solders up a sealed box for his sister's jewelry and embeds it into some of the concrete ballast of the boat. Keith agrees to keep his 10-year-old niece until her parents make it to Vancouver.
Months later, word comes that the ship has run into a reef near Tahiti. Two bodies were found, and all that was left of the sailboat are the keel and some concrete bits. Their will makes Keith trustee of his niece's inheritance... all 56 pounds of it. Her parents had apparently sold off everything they had and converted it into diamonds before they left.
That jewelry box belongs to his niece, and it's his duty to retrieve it for her if he can... but Keith is a man who seldom leaves his house. He has no passport, no car, no relatives he can impose on, and almost no money. He doesn't even have any close friends; just some casual acquaintances among the local model engineering hobbyists. So he starts calling up the only people he knows...
Today we'd call it "networking". And that's really what the book is about; how a reputation can precede you, and a dash of "six degrees of separation."