Matt Letscher has signed on to guest star in the premiere episode of "Castle" Season 7. The premiere episode is titled "Driven" and Kate Beckett will be seen working on the hardest case of her life, the disappearance of her fiancé Rick Castle.

The Season 6 ended with bride Beckett at an accident spot. Castle's car was in a ditch and in flames. Castle never made it to their wedding. The new episode will open right where it left off and Beckett will soon find that Castle's body is not inside the burned-out car. This is set to kick-start the investigation to find what happened to Castle.

TV Line reports that Letscher, who played Billy Chambers in "Scandal," has been roped in to play the character called Henry Jenkins, a security consultant. Jenkins "provides Beckett with information on the most important case [Castle's disappearance] of her life," according to TV Line.

In its earlier report, TV Line described this character as a "highly intelligent yet unassuming gent who's deft at blending into a crowd."

As reported previously, Ryan Sands has been cast as a police sergeant of Hamptons, Tagger. TV Line reported that Tagger will be seen helping Beckett investigate the "most difficult case of her career." And, a doctor, a shrink and a Coast Guard captain are also expected to make an appearance in the premiere episode.

There is expected to be a "significant" time jump in the premiere episode. It looks like Beckett's investigation will hit a dead-end. It is only after some months that she and Castle's family are likely to find out about what happened to Castle.

The new season of "Castle" will introduce a new mythology that revolves around Castle. New secrets related to him will be revealed. This is going to cause friction in Castle and Beckett's relationship. However, this couple's relationship will continue to remain strong. The whole truth about Castle's disappearance would be revealed over the course of Season 8, not in the premiere episode.

David Amann has written the premiere episode of Season 7 and Rob Bowman has donned the director's hat.

"Castle" Season 7 returns on Sept. 29, 2014 on ABC.