This Thing of Darkness (published in the United States as To the Edge of the World) was the debut novel of Harry Thompson, published in 2005 only months before his death in November of that year at the age of 45. Set in the period from 1828 to 1865, it is a historical novel telling the fictionalised biography of Robert FitzRoy, who was given command of "HMS Beagle" halfway through her first voyage. He subsequently captained her during the vessel’s famous second voyage, on which Charles Darwin travelled as his companion.