In one section of his 24-minute long episode, he can be seen exploring different parts of the building – which has been untouched since 1980 – including a large atrium area with a large glass roof above it.
As he is about to enter a door, a noise that sounds like a woman’s scream can be heard in the background.
Dee then pans the camera round to reveal a ladder, saying: “I ain’t going up there.”
Speaking to LADbible, the Youtuber said that, at the time, he hadn’t heard the sound and only noticed it when he was watching the footage back.
He explained: “I went alone and when I was there there was nobody else inside the building so had the full asylum to myself, I was there for roughly two hours.
“I never noticed the scream until I was editing the video back ready to be uploaded. And was horrified that it was so loud and clear that I never heard anything in real time.”
On hearing it back, the 26-year-old said: “I 100 per cent believe it was an ex-patient screaming for help or that their spirit is trapped there.”
At one point during filming, Dee said he had to take a break as he felt as if he was being watched and began to get scared.
He also explained that he felt the presence of people at other points during his time there, despite being alone. For example, in the basement, he felt the sensation of someone walking past him.
Dee said: “It was cold down there, and you would get breezes as if someone had just walked past you.”
He added: “I did notice when I was there a few moaning noises and women talking but I kind of ignored it and didn’t want to get scared as I was alone and the place was so big.
“I heard a moan, and captured it on camera too, that place is most definitely haunted.”
All we can say is, scream or no scream, we wouldn’t be caught dead in that place.