In the town of Friendship, Maine, two young boys named Nicky and Andreas enter a creepy, old mansion called Whipstaff Manor, apparently on a dare, but they are scared away by a ghost named Casper. Later, after the death of her father, neurotic and spoiled heiress Carrigan Crittenden discovers he has only left her Whipstaff Manor in his will. Carrigan and her assistant, Dibs, learn of a treasure allegedly hidden somewhere within the manor, but upon investigation, they find the manor haunted by Casper and his obnoxious prankster uncles, the Ghostly Trio, who scare the two off the property. The two make several attempts to force the ghosts out of the manor by way of paranormal experts and a demolitions team, to no avail. Meanwhile, a lonely Casper watches a news report of paranormal therapist James Harvey and is instantly smitten with his teenage daughter, Kat. Longing for a friend, this provides Casper the idea of inspiring Carrigan into summoning Dr. Harvey to Whipstaff. Harvey and Kat have an estranged relationship due to the former's reputation and obsession with contacting the ghost of his late wife, Amelia. Moving into Whipstaff, Casper's attempt in befriending the Harveys fails when his uncles try to scare them out of the house.