Glamis Castle is said to be one of the most haunted castles in Great Britain. It is even mentioned in Macbeth, although the real King Macbeth never lived there and the castle as it is now, was built long after his death. That doesn't matter though, the castle has enough history of its own.
There are reports of ghosts, secret passages leading to secret rooms, scandals, bizarre initiations and monsters. The difference between the truth and legends for many of these tales is hard to define with the passing of centuries but even so, it makes for good reading.
One of the ghosts, rumoured to be that of Lady Janet Douglas, is said to haunt the clock tower. Lady Douglas was burned at the stake after being accused of poisoning her husband.
The most famous legend is that of the Monster of Glamis. There is dispute regarding who the monster was but the central core of the story is of someone being hidden away in a secret room. This isn't too hard to believe, in some places the walls are 16 feet thick.
Whatever the secret was, it is stated that only three people were allowed to know it at a time; The Earl, the Earl’s heir, and the estate manager.
One theory is that a rival clan was locked in a windowless room which was then sealed. The clan eventually died and the secret passed down to ensure the room was never reopened.
The most popular theory though, revolves around Thomas Lyon-Bowes who, it is reported, died on the same day he was born. The midwife though, claims he was in good health when she left despite being born deformed. His death was announced the next day leading some to assume he was hidden away so his family wouldn't have to live with the shame of a disabled child.
Another contender is a child who was also reported to have died young. A painting exists of the 3rd Earl of Strathmore and his three sons. The problem is that only two of his sons ever reached the age at which they are depicted in the painting. Could this child have been hidden away also?
Sources
https://en.wikipedia.org/wiki/Thomas_Lyon-Bowes,_Master_of_Glamis_(born_1821)
https://www.ancient-origins.net/ancient-places-europe/dark-secret-behind-hidden-room-glamis-castle-006821
https://www.smithsonianmag.com/history/the-monster-of-glamis-92015626/