Cast and characters
- Pamela Sue Martin as Nancy Drew
- Shaun Cassidy as Joe Hardy (credit only)
- Parker Stevenson as Frank Hardy (credit only)
- George O'Hanlon, Jr. as Ned Nickerson
- Jean Rasey as George Fayne
- William Schallert as Carson Drew
- Monte Markham as Professor Jack Wall
- Robert Karnes as Sheriff King
- Arthur Peterson as Old Man Jensen
- Skip Ward as 2nd Agent
- Joe Penny as Brandon
- Ron Nyman as 1st Agent
Nancy dances with Brandon at his party, while George encourages Ned to tell Nancy how he feels. The four of them go out on Brandon's boat, and Nancy notices that a lot of the fish are floating dead, and a light in the lighthouse tells them that someone is there but it should be abandoned. They turn back to the party.
Nancy, George, and Ned meet the sheriff at the lighthouse, but the sheriff doesn't see how anyone could get into the lighthouse and doesn't believe them. As they drive away, someone watches them from a window.
Carson Drew and Ned discuss Nancy's investigation and that the lighthouse is being purchased by Professor Wall. Ned leaves to check on Nancy, who's investigating the lighthouse.
At the lighthouse, George saws through the lock and Nancy finds tire tracks in the ground outside. The inside of the lighthouse appears long-abandoned, but Nancy finds footprints in the dust. George runs into Professor Jack Wall outside, who tells them he's researching ghosts. He invites them to join his research at the lighthouse that night.
Nancy asks her father to spend the night in the lighthouse, along with George, and he approves despite Ned's objections.
Nancy and George talk about how they've never heard any rumors about the lighthouse being haunted, and Nancy wonders how the Professor heard any. The Professor tells them the old story about their lighthouse and shows them an old book. But Nancy is skeptical of his story because the date his book was checked out from the library doesn't match the timeline he told them.
That night, Nancy and George meet the Professor at the lighthouse where he's set up his equipment. The Professor tells them more ghost stories. After three hours, the equipment allegedly detects activity, but Nancy realizes it's a trick with a tape recording and she exposes the hoax. She realizes the Professor is after treasure, but Ned's contract excludes anything found underground.
They talk with Carson Drew, who agrees to sell the lighthouse and all bounties under the surface for double the price plus 10% of anything found. Professor Wall accepts the offer. Nancy wants to return to the lighthouse because not everything is answered, such as how the footprints disappeared.
Nancy and Ned look outside around the lighthouse and find a new cave entrance blown open, which would account for the dead fish they saw. They find a door that Ned estimates is from 1930s for smugglers. They break through the door and find a skeleton. The tide starts coming in and they can't get out the way they came in, so they continue through the cave and come to a metal door. Professor Wall hears them on the other side of the door, but doesn't make his presence known. While trying to get through, Nancy discovers a secret room above them where treasure is hidden. Professor Wall finally opens the metal door, "rescuing" Nancy and Ned.
George returns from New York with a photocopy of the same book the Professor was using, and Nancy realizes that the map is different.
Nancy confronts Professor Wall at the lighthouse. She thinks he planted the treasure and he made up the story about their lighthouse to launder money he obtained illegally. Professor Wall chases Nancy out by cliffs, but the police arrive in time. It turns out that the police have been watching Professor Wall for three years, and they finally have what they need to arrest him.
Carson Drew, Nancy, George, and Ned return from dinner, and Nancy tells them that Professor Wall converted his money to old coins by purchasing them through mail orders, which she found out by reading Professor Wall's confession in the newspaper.
- on The Internet Movie Database