"Phantom Piper" is the fourteenth episode of the first season of Supercar. It originally aired on ATV in the United Kingdom on April 29, 1961.
The episode opens in a castle in Scotland, where strange bagpipe music is heard. The music wakes a young girl named Vilicity, who thinks it might be something called the Phantom Piper. However, she soon sees the window opening and closing from the wind. But, the bagpipe music is soon heard again. Meanwhile, a man named Dr. Horacio Beaker is reading a book when the phone starts ringing. Once he picks it up, he hears bagpipe music in the background. Turns out, the call is coming from his cousin Vilicity, the girl from earlier.
Horacio asks what's with the noise, and Vilicity explains that it's his great uncle Angus playing the bagpipes. Vilicity explains the problem, then Horacio explains it to Mercury Man of Supercar. It's also revealed that the appearance of the Piper is an ill omen. Meanwhile, Vilicity hears that the Phantom Piper has been heard for over 200 years, ever since the castle was attacked and plundered in 1750. Meanwhile, the Supercar team leaves for Scotland.
After a 7 hour flight, the Supercar team arrive in Scotland. The first place they examine is the southern battlements, where the piper has been known to appear. Later that night, uncle Angus starts playing the bagpipes. However, when the clock strikes midnight, and uncle Angus has ceased playing the pipes, some other bagpipes are heard. When Mercury and Horacio hear the music, they check on the screen inside Supercar, and spot someone playing the bagpipes.
The next day, Mercury rationalizes that what he and Horacio saw wasn't a transparent ghost, but a solid person. Mercury also theorizes that whoever it is, he might be planning to steal something, though there's really nothing valuable in the castle. However, uncle Angus says that there is something in the cellar, though not of great value. It is actually a chunk of sterling, worth only $40, or 15 pounds. Mercury then notices the thick bars surrounding the sterling have been filed, meaning that someone tried to get it, and might try again that night.
Once night has fallen, the Supercar team puts a plan they made into action. The plan is: wait until the piper starts playing again. And once he does, Angus and Vilicity head down to the cellar to find out who's been filing the bars protecting the sterling. Once midnight strikes, the phantom piper begins to play. Mercury and Horacio spot the piper, and scare the pants off of him.
Meanwhile, Angus and the others head down to the cellar and apprehend the culprit, while Mercury and Horacio apprehend Mr. Harper, who disguised himself as the Phantom Piper in order for the thief downstairs to file the bars without attracting attention. However, Horacio reveals that the sterling is actually topaz, and worth half a million dollars! Horacio then reveals that Mr. Harper got his pipe recording for his ghost act by hiding the recorder in the castle and taping Angus whenever he played the pipes.