

Though a game to the three Drews, the importance of the manuscript begins to surface, first when a mysterious man and a woman claiming to be his sister appear and ask the Drews about secret passages and maps, then even more so later when the house is burglarized while the Drews sleep. While exploring the massive house that Uncle Merry, Meriman Lyon to the wider world, the three Drew children, Simon, Jane and Barney, discover an ancient manuscript which they believe to be a map showing the location of what they believe to be an ancient treasure. Over Sea, Under Stone opens with the Drew family, Dick, Ellen and their three young children, arriving in Cornwall for a summer vacation, which they'll be spending with their Great Uncle Merry, a mysterious professor who often appears unexpectedly on the Drews' doorstep to vanish just as quickly in the night.

It wasn't until about ten years later that I got the proper skinny on it and read the series in proper order.

I actually started this series, although I didn't know it was such at the time, back in 1993 whenI was in Junior High, with the fourth volume.
