In the novel, Quincey hailed from Texas and was one of Lucy Westenra's suitors. He helped fight Dracula after her vampirization and death. He died in the struggle, having been stabbed by one of Dracula's gypsy servants.
In the Castlevania series, Quincy is a relative of the Belmont Clan through the Morris Clan. The game's account of the novel likely differs from the novel itself in many regards.