Fans of CBS' "Elementary" can add another entry to its list of cast members to look forward to. It has been revealed that Owain Yeoman has been tapped to play a character in the 100th episode of the series.

The 100th episode, titled "Henny Penny The Sky Is Falling," will premiere on Oct. 30. According to TVLine, the Welsh actor will be guest starring as an old boarding school classmate of Holmes' (Jonny Lee Miller) and is now a scientist. Holmes will turn to his character, described as "fun and very colorful," for help with a case.

As for the story of the 100th episode, executive producer Rob Doherty teased that it "revolves around the murder of a man who was looking for better and more efficient ways to identify what are known as Earth-killer asteroids."

"So there's mystery on top of mystery as to why anyone would want to kill someone who might be able to help NASA locate and, hopefully, divert a small planetoid hurdling towards Earth," he continued.

Yeoman is known for his roles on "Extant," "Turn: Washington's Spies," and "Supergirl." Most notably, the 38-year-old actor appeared as a regular on another CBS series, "The Mentalist," playing agent Wayne Rigsby.

It was previously reported that another famous name will guest star in the fifth season of "Elementary." Nelsan Ellis has been cast as Shinwell Johnson, a reformed drug dealer who has a history with Joan (Lucy Liu). Shinwell will aid the two detective partners in a case, but will find himself wrestling with the temptation of going back to his old ways.

Additionally, Virginia Madsen will be reprising her role as Paige. Fans know that Paige is Gregson's (Aidan Quinn) love interest on the show. The couple have had a rocky relationship, but Doherty has said that theirs is a growing one. 

"Elementary" season 5 will air its premiere episode, titled "Folie a Deux," on Oct. 2 on CBS.