Nothing is known about the Floating Head's life, who he was or how he died.
Following his death, the Floating Head's spirit remained on earth and unable to move on, due to unknown unresolved issues. During Dr. Zorba's travels around the world, he met and captured the Floating Head and imprisoned him in his mansion.
When Dr. Zorba was murdered and became the twelfth ghost, Cyrus Zorba and his family moved into the mansion. One night, when Cyrus investigates the cellar and puts on the spectral viewers, the Floating Head and three of the other ghosts appear to him.
The Floating Head and the other eleven ghosts presumably crossed over when Benjamin Rush died and became the thirteenth ghost.