The best thing about the treasure is that it is hidden somewhere, probably in a crypt, on the Island of Jersey in an area dotted with ancient ruins and dominated by a striking cliff-top castle. The best thing about the book is its well-etablished romantic mood (the author, it will be remembered, has done both adult mysteries as well as juvenile novels). A Nazi war criminal masquerading as a professor is the villain, and a dangerous one as the children who are after him come to realize. They are an intriguingly polyglot group (Jersiaise, Finnish, French) and the adventure acquires momentum as the narrative alternates from one to another. The actual mystery is slight and contrived, but it will have a certain aura for the girls.