A child prodigy comes to stay with the Wheelers. Trixie and Honey go into the marsh to gather specimens for a school project. These two things add up to a mystery, of course.

Trixie Belden and the other members of the Bob-White club visit her uncle's farm in Iowa, where they catch the thieves who had been stealing sheep in the area. 

Great-headed man, with a blinking eye, A shaded road, a horse's cry, Foreign words for all to hear, First clue is now so very near, Watch out for thieves; they're everywhere, At home, on island, dead beasts' lair. Where shines a beacon 'cross the sky, Beware, great danger lurks close by. Thus begins the strange prophecy that launches Trixie and the Bob-Whites on another adventure.

Jim Frayne discovers he has a cousin, Juliana, an heiress to a small fortune and then she shows up in Sleepyside to claim it. meanwhile, Trixie and the gang befriend an amnesiac young woman called Janie whom somebody seems to want to harm.

"When Trixie could stand the waiting no longer, she went after Bobby. The instant she opened the kitchen door, she was grabbed. She just had time to scream before the voice growled, "Shut up, or you've had it!" A hand clamped over her mouth ..."--Page 4 of cover

While trying to help a widow who grows flowers for a living, the Bob-Whites discover that an illegal planting of marijuana is the source of many of the problems that have been plaguing her.

When a baby mysteriously appears in the Beldens' dog house, Trixie and her friends become involved in helping the local police try to find the baby's older brother, who they fear may have been kidnapped.

When a strange writer haunts the Hudson River area near Trixie's beloved Sleepyside and her brother begins to manifest some mysterious and frightening symptoms, Trixie decides to investigate. Brian is poisoned and Trixie suspects his lab partner is responsible. Also, she spots a shark in the Hudson river! And then she meets an odd children's author who has a deep interest in sharks. What can it all mean?

When Miss Trask returns to her hometown, the gang tags along and stays at Pirate Inn, owned by Miss Trask's brother. Legend is that a ghost ship appears whenever something bad is about to befall the Trask family and sure enough, a ghostly galleon shows itself to Trixie and Honey and soon Mr. Trask vanishes, leaving the future of his business in doubt.

Trixie Belden and the other members of the Bob-Whites of the Glen go camping in northern Idaho, and their camp is visited by a sasquatch.