The English seem to have an endless supply of able writers, devilish school-boys and ancient battlements. In this mystery adventure, David's friends, Arthur and Peter, devise an elaborate plot to get on the church roof, which David can't scale because of a shortened leg. The plot fails, but in escaping capture the boys uncover an old town newspaper, dated 1914, that arouses their curiosity about Colonel Sheperton, whose grandfather clock has stood in David's father's (and grandfather's) shop since that date. Why did Colonel Sheperton make secret voyages in the timber ships? Why did he telephone David's grandfather to take the clock on the very day in 1914 that he died in his burning house? After much investigation, the boys discover that the Colonel was a British spy killed by German sailors to prevent his transmitting secret information, and that the information is still in the clock. In the meantime David's longer leg has been shortened to make the two match, a possible operation but a questionable episode. (David's resentment at his handicap is mollified only by the promise to remove the handicap.) Newly agile, he helps his friends thwart a gang of robbers taking lead from the church roof.... Middling mystery, supported by lively dialogue, well-developed incidents (with the above exception), and the stout stone walls of an interesting old town.