Tom Tomsky, a timid nine-year-old, reluctantly agrees to help professional ghostbuster Hetty Hyssop find the Incredibly Revolting Ghost that is haunting the Averagely Spooky Ghost hiding out in Tom's attic.
While acting in a "haunted house" featuring interesting deaths in history, Ellen is contacted by the ghost of a former resident, who seems to be protecting the collection of antique Wedgwood dishes on display there.
When Allie is contacted by the ghost of a dog, she and Dub investigate the surly new boy at school and his father, who may be running a puppy mill, to see if they are involved.
During a summer in an abandoned mining town, Katie's relationship with a rebellious stepbrother improves as they probe the past to find out why there seem to be ghosts, literally, beneath their feet.