Sherlock (Jonny Lee Miller) and Joan (Lucy Liu) are going to hunt a mass murderer in Season 5, Episode 6 of “Elementary.”

According to the synopsis for the episode, titled “Ill Tidings,” the crime-solving duo finds themselves investigating a mass murder when a chef and his customers are poisoned after dining on a tasting menu contaminated with snake venom.

As seen in the preview clip for the episode, a busy restaurant kitchen becomes an instant crime scene when a chef suddenly falls to the ground. Shortly thereafter, Sherlock and Joan find out that several of the chef’s patrons also died after dining at the restaurant.

Sherlock’s love interest, Fiona (Betty Gilpin), also makes her return to the series in the episode. According to the synopsis, Detective Bell’s (Jon Michael Hill) crush on a work colleague makes Sherlock realize that his and Fiona’s relationship is at an important crossroads.

In an interview with Entertainment Weekly last September, executive producer Rob Doherty announced that Gilpin is reprising her role as Fiona this season.

“We certainly owe a status report for the Sherlock/Fiona relationship,” Doherty said at the time. “In the first few episodes there won’t be much mention of her, but we are working on a return for Betty Gilpin. Fiona is a thread that we won’t let dangle too long, especially considering how much we love Betty.”

Gilpin made her first appearance on the show in Season 4, Episode 9, titled “Murder Ex Machina,” in which Sherlock and Joan met her character for the first time during a murder investigation.

It was then revealed in Season 4, Episode 18, titled “Ready or Not,” that Sherlock and Fiona had been dating. But when Fiona felt that Sherlock was acting different around her, she decided to end their relationship.

Later in the episode though, Sherlock admitted to Fiona that he was just being careful because he’s never been in a serious relationship before. Fiona understood where the detective was coming from, and the episode ended with the two consummating their newfound connection.

Are you excited for Fiona’s return? Sound off in the comments below!

“Elementary” Season 5, Episode 6 airs on Sunday, Nov. 13, at 10 p.m. ET on CBS.