When Meg Langslow's grandfather is booked by a cruise line to give lectures on birds, she and other family members join him. In this 25th outing (after Lark! The Herald Angels Sing), they find themselves broken down in the Bermuda Triangle, and worse yet, a woman has jumped overboard, and grandfather's assistant Trevor seems to have gone missing, too. The captain decides not to investigate, but Meg's father thinks they should find out whether there was foul play while the prime suspects are all stuck on board. It'll be a race against the clock to solve these mysteries before they make the necessary repairs and return to shore.