Joan Watson (Lucy Liu) will prove that resourcefulness can save the day as she and Sherlock Holmes (Jonny Lee Miller) deal with more cases in "Elementary" season 5.

CBS revealed the synopsis for the premiere episode of the show's upcoming installment titled "Folie a Deux," where Watson will reconnect with an old acquaintance to help her and Holmes solve a big case.

The synopsis for the episode reads:

"In the season premiere, Holmes and Watson join the NYPD manhunt for a serial bomber who is active again after going dormant for six years. During the investigation, Watson seeks help from a former criminal, Shinwell Johnson (Nelsan Ellis), whose life she saved when she was a surgeon."

According to reports, Johnson might be willing to do an undercover job to infiltrate criminal groups so he can get more information to help the duo find out where the serial bomber is hiding.

Meanwhile, Sherlock will have an accomplice of his own in the 100^th episode of the police procedural crime drama.

TVLine revealed that "The Mentalist" alum Owain Yeoman will appear in the episode titled "Henny Penny The Sky Is Falling" as Sherlock's former boarding school classmate turned scientist.

Executive producer Rob Doherty revealed that Yeoman's character will help solve the murder case where another scientist ended up dead.

Doherty teased that the episode "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."

To solve the case, Sherlock's old friend might give him leads to find out what really happened to the victim.

"Elementary" season 5 is slated to premiere on Sunday, Oct. 2.