Dr. John Polidori (1795-1821) wrote what has become one of the first major works in horror. He's most famous for having written "The Vampyre" in 1819, the first English vampire story.
At only 19 years old, he wrote an essay on sleepwalking and received a doctor of medicine from the University of Edinburgh.
A year later in 1816, he met Lord Bryon and began traveling with him. He was given the job of journaling the adventures by a publisher. This was the same year that they spent a weekend with Mary Shelley, her husband Percy Shelley and Mary's sister Claire Clairmont. (this is the famed weekend both wrote The Vampyre and Frankenstein)
Polidori soon went on to write a poem called "The Fall of Angels" which was published in 1821. He had published more then a few medical essays before venturing into the world of fiction, but they were all out shined by his short "The Vampyre".
In 1911, the journal he'd been paid to keep of his time in the employ of Byron, was published; but only after his sister had edited to her standards, removing most of what she found to be "questionable behavouir".
Dr. John Polidori committed suicide by drinking poison in 1821