In 1944, a small town in Illinois was gripped with fear that someone was spraying a toxic gas into their homes as they slept. And while there have been several explanations, there isn’t any one that’s recognized or accepted as the truth. 
Research:

“‘Anesthetic Prowler’ Covers City.” Journal Gazette. Sept. 5, 1944. https://www.newspapers.com/image/93681179/?terms=%22Urban%20Raef%22%20&match=1
“‘Anesthetic Prowler’ on Loose.” Journal Gazette. Sept. 2, 1944. https://www.newspapers.com/image/93681104/?terms=%22%27Anesthetic%20Prowler%27%20%22%20%20Loose.%22&match=1
“At Night in Mattoon.” Time. Sept. 18, 1944. https://web.archive.org/web/20080306220348/http://www.time.com/time/magazine/article/0,9171,796678,00.html
“Carbon Tetrachloride Poisoning.” Centers for Disease Control. https://www.atsdr.cdc.gov/csem/carbon_tetrachloride/docs/Carbon_Tetra_Patient_Ed_Sheet-508.pdf
Chaplin, James Patrick. “Rumor, Fear, and the Madness of Crowds.” Ballantine Books. New York. 1959. Accessed onling: https://archive.org/details/rumorfearmadness00chap/page/10/mode/2up
Fopay, Dave. “’Mad Gasser’ Author Points Finger at ‘Brilliant’ Chemistry Student.” Journal Gazette. June 30, 2003. https://www.newspapers.com/image/84792181/?terms=%22Farley%20Llewellyn%22%20&match=1
“History of Coles County.” Coles County, Illinois Homepage. https://www.co.coles.il.us/genInfo.html#:~:text=Mattoon%20was%20founded%20as%20a,Stephen%20Doles%20and%20Ebenezer%20Noyes.
“’Hysterical Mistake,’ Police Say of Mattoon’s Gas-Spraying.” Sun-Telegram (Richmond, Indiana). Sept. 13, 1944. https://www.newspapers.com/image/253218677/?terms=%22Atlas%20Imperial%20Diesel%22%20Engine&match=1
“Intensify Hunt For Paralysis Gas Prowler” Mattoon Orders Police on 24 Hour Watch.” Chicago Tribune. Sept. 7, 1944. https://www.newspapers.com/image/370374182/?terms=%22anesthetic%20prowler%22%20&match=1
“Is ‘Madman od Mattoon,’ Who Gasses Victims, Real or Result of Comic Book Imagination?” Press and Sun Bulletin. Sept. 8, 1944. https://www.newspapers.com/image/260955754/?terms=Beulah%20Cordes&match=1
Johnson, Brooke. “Author Claims to have solved ‘Mad Gasser.’” Journal Gazette. March 22, 2003. https://www.newspapers.com/image/84639401/
“Mad Anesthetist Keeps Town Awake.” Independent. Sept 8, 1944. https://www.newspapers.com/image/718770228/?terms=Beulah%20Cordes&match=1
“Madman of Mattoon: 2 More are Victims of Phantom Prowler.” The Times Herald. Sept. 9, 1944. https://www.newspapers.com/image/209765891/?terms=%22%27Anesthetic%20Prowler%27%20%22%20%20Loose.%22&match=1
Maruna, Scott. “ The Mad Gasser of Mattoon: Dispelling the Hysteria.” Swamp Gas Book Company. 2003.
Hereford, Robert A. “Mattoon Argues Over Denial That Prowler Exists.” St. Louis Star and Times. Sept. 13, 1944. https://www.newspapers.com/image/205455415/?terms=%22Atlas%20Imperial%20Diesel%22%20Engine&match=1
“Police Get Two False Alarms During Night.” Journal Gazette. Sept 13, 1944. https://www.newspapers.com/image/93681538/?terms=%22Police%20get%20two%20false%20alarms%20during%20night%22&match=1
“Prowler Sprays Fumes Which Cause Paralysis.” Times-Tribune. Sept. 7, 1944. https://www.newspapers.com/image/534404923/?terms=%22anesthetic%20prowler%22%20&match=1
“Some Say ‘Madman of Mattoon’ Is Hoax.” The Dispatch. Sept 8, 1944. https://www.newspapers.com/image/340095570/?terms=Beulah%20Cordes&match=1
Waters, Dustin. “The mystery of the ‘Mad Gasser of Mattoon’ who terrorized an Illinois town.” Washington Post. Oct. 30, 2021. https://www.washingtonpost.com/history/2021/10/30/mad-gasser-mattoon-illinois-mystery/
“Wave of Hysteria Hits Mattoon; Police Watch Amateur Chemist.” The Palladium-Item. Sept. 12, 1944. https://www.newspapers.com/image/253218459/?terms=%22Aline%20Kearney%22%20&match=1
“We face the future knowing we have won … Staunch Friends.” Journal Gazette. Sept 26, 1944. https://www.newspapers.com/image/93682148/?terms=atlas%20diesel&match=1
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