Hardy Boys book twelve, as updated in 1965, sees the sibling detective teenagers rescue a man who has fallen overboard, and who gives them a cryptic warning about footprints before disappearing. It's a good adventure story that includes some international travel.

Parts of the story feel dated, and to an adult reader a little bit odd - as in one of the earlier stories, references to unfriendly countries are vague and don't feel a natural part of the narrative. On the other hand, they added a little grandeur to the story that some of the earlier books were lacking with an over reliance on a particular type of criminal.