Books in The Mystery of series

"The Secret of Thunder Mountain" (#6), utilizes Gulliver's Texas ranch as a setting- a ranch that Gulliver seems to spend precious little time on. Here a cavern in a nearby peak is being utilized by ruthless killers who robbed an armored car of three million dollars in gold several years before. At Thunder Mountain the gang have high-powered electric furnaces to melt the gold and local rocks together to form an appearance of ore which they then hope to be able to "legitimately" reprocess without suspicion. But their huge electrical generators and furnaces produce a loud static interference on television and high-frequency radio bands, and in an effort to track down the location of this static in order to help out a friendly old man whose television reception is being ruined, Tom builds a radio direction-finder which is, incidentally, described with complete technical accuracy. (In fact, as a boy, I once built a similar one after reading this book.) Plotting on a map from two different locations the directional readings for the static, Tom finds that the two lines on his map meet at Thunder Mountain. This book contains some of Fran Striker's very best writing, from the descriptions of Hamilton Quest's somber victorian apartment in New York City to the killer waiting in the weeds of a vacant lot in Texas, sweating in the hot sun and slapping at a bug on his hand. The tone, detail, and pace of this book are unsurpassed.