Three young women from the US believe they are exorcists and have visited the "spiritually polluted" UK to try to rid the nation of Satanic demons.
Brynne Larson, 19, and sisters Tess and Savannah Scherkenback, 19 and 21, think that a large proportion of the world's population is possessed by evil spirits that cause depression, addiction and suffering.
In a BBC3 documentary, filmmakers follow them as they visit what they believe to be one of the most spiritually corrupt places in the world - London.
The teenage exorcists explained: "It's been centuries in the making but it all came to a peak with the Harry Potter books that have come out and the Harry Potter rage that swept across England."
Tess continues: "The spells and things that you're reading in the Harry Potter book, those just aren't something that are made up. Those are actual spells. Those are things that came from witchcraft books."
"Harry is using this magic for good, so here we have the dangerous idea that you can use magic for good or bad, when in reality all magic is bad because you're getting your power from Satan," Brynne says.
The women say they are in the UK to "kick some demon butt" and are "horrified by the sense of evil" across the country, the Mirror reported.
"The people of England are under such heavy attack by the enemy," Savannah said.
They explain that the first stage of exorcism is getting the demon to the surface. They must then lay crucifixes on the possessed person's head and then command it into the pit of hell. In total, the women have performed more than 100 exorcisms.
During the film they perform an exorcism on Beth Wragg, a 36-year-old woman who claims to have been possessed since she was born. During the exorcism, she is thrown into convulsions and screams while the women battle the demon.
"I can't explain it but I do believe I've been exorcised," she said afterwards. "I feel a different person. I have more energy."
The group's mentor is Brynne's TV evangelical father Bob Larson, who takes them across the world performing exorcisms.
Sceptics say their mission is purely about making money. Larson's website is full of merchandise that offers people merchandise and features a test to see if you are possessed. He charges £200 per exorcism.
Filmmaker Dan Murdoch spent six months with the women for the documentary. He told the newspaper: "Whether you think exorcism is taking advantage of the vulnerable, a form of therapy or a genuine miracle, it seems to have at least a short-term effect on some people - and after spending six months with the girls I don't think they're frauds."
All three appear to believe in their powers of exorcism. Savannah says their karate abilities help them to battle the forces of darkness. Brynne adds: "We can defend ourselves and also fight battles. My special skill is as the enforcer. I can take on demons."
The Teenage Exorcists is on BBC3 at 9pm tonight (Thursday).