What follows below is indeed a true event, verifiable by multiple sources.
On July 2, 1951, at about 8:00 AM in St. Petersburg, Florida, Mrs. Reeser's landlady came to give a Mrs. Mary Reeser a telegram and some coffee, when she found that the metal doorknob was hot to the touch. After enlisting the help of some carpenters working nearby, she eventually forced the door open. Inside, they found the cremated remains of Mrs. Reeser. Most of her body were in ashes, the only surviving parts being her backbone and left foot (still with a slipper on it). Her skull was also found, shrunken to "the size of a teacup," with all facial features removed.
After calling the police, an investigation was launched by the local police chief, J.R. Reichert. The investigation found that, although Reeser's body was totally cremated, the rest of the room was largely unaffected. Only a few appliances had been melted and made soft due to the heat. A socket had also melted, stopping a clock at 2:26 AM. The police were baffled that a fire that caused so much damage to Mrs. Reeser (the temperature was estimated at 3000 Degrees Fahrenheit) could leave the rest of the house, indeed much of the room intact. During the investigation, Reichert sent FBI director J. Edgar Hoover to take several items from the crime scene, including glass fragments found in the ashes, small, charred pieces of teeth, some carpet, and the slipper. In response, Hoover sent a team of FBI investigators and physical anthropologist Wilton Krogman, as well as notifying President Harry S. Truman.
After weeks of investigation, the FBI declared that Reeser had died due to the wick effect. As a known user of sleeping pills, they concluded that she had fallen asleep while smoking, and set fire to her nightgown. They reasoned that the human body has enough fat and other inflammable substances for the body to be set alight, like a candle. This would therefore allow large amounts of destruction. However, both Reichart and Krogman disagreed on the conclusion made by the FBI. Krogman remarked that "I find it hard to believe that a human body, once ignited, will literally consume itself -- burn itself out, as does a candle wick, guttering in the last residual pool of melted wax [...]
"Just what did happen on the night of July 1, 1951, in St. Petersburg, Florida?
"We may never know, though this case still haunts me," and, on the shrunken skull, he wrote "[...]The head is not left complete in ordinary burning cases. Certainly it does not shrivel or symmetrically reduce to a smaller size. In presence of heat sufficient to destroy soft tissues, the skull would literally explode in many pieces. I have never known any exception to this rule." After finally concluding that "I cannot conceive of such complete cremation without more burning of the apartment itself. In fact the apartment and everything in it should have been consumed. [...] I regard it as the most amazing thing I have ever seen. As I review it, the short hairs on my neck bristle with vague fear. Were I living in the Middle Ages, I'd mutter something about black magic." Krogman then put forward the idea that Reeser was murdered with crematorium equipment, but with no explanation for the melted appliances.
We may never know who or what caused Mary Reeser to ignite in her armchair, on July 2, 1951, at 2:26 a.m. Whether you believe in the paranormal or in spontaneous human combustion, the case does tell us this: "Perhaps truth can be stranger than fiction."