"Gabriel Knight is a series of adventure games produced by Sierra On-Line in the 1990s. Three games were released in the series: Gabriel Knight: Sins of the Fathers, The Beast Within: A Gabriel Knight Mystery and Gabriel Knight 3: Blood of the Sacred, Blood of the Damned.
One compilation was released: Gabriel Knight Mysteries: Limited Edition. It included the first two games in the trilogy.
The Gabriel Knight characters and games were created by writer Jane Jensen, who also worked on King's Quest VI: Heir Today, Gone Tomorrow with veteran game designer Roberta Williams. All three games in the series focus on the adventures of Gabriel Knight, a New Orleans author and bookstore owner who finds that his destiny is to become a Schattenjäger, or "Shadow Hunter". Gabriel's assistant, sidekick, and sometime romantic interest Grace Nakimura is a major supporting character in Sins of the Fathers. In The Beast Within and Blood of the Sacred, Blood of the Damned, she shares the role of protagonist with Gabriel. The player alternates between Gabriel and Grace for different portions of each game.
With a balanced mix of historical facts and fictional elements, as well as an emphasis on character development (e.g. the relationship between Gabriel and Grace is an important subplot throughout the series), the Gabriel Knight games have been praised as outstanding achievements in storytelling. The music in the series, composed by Robert Holmes (Jensen's husband), contributes significantly to the atmosphere."
Source: Wikipedia, "Gabriel_Knight", available under the CC-BY-SA License.