Nicole Frederick documentary.
"The Life And Career Of Thelma Todd" says that Thelma Todd was in "The Devil's Circus". A search found this item on the Wikipedia entry for "The Haunted House":
After his success in Europe with his 1922 film Haxan, director Christensen relocated to Hollywood in 1926, where he directed Thelma Todd in The Devil's Circus who would appear again in The Haunted House.
- Workman, Christopher; Howarth, Troy (2016). Tome of Terror: Horror Films of the Silent Era. Midnight Marquee Press. ISBN 978-1936168-68-2.
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There were two men arrested for writing the extortion notes, but the authorities said that the second man was the one who actually wrote them. He was sent to an insane asylum.