A map, a body, and concealed information all combine to bring Joan back on the case in this week’s Elementary season 3, episode 6, “Terra Pericolosa.”

“Terra Pericolosa,” or “vacated land,” will be the focus of this week’s case on Elementary. A map, seemingly boring, unless of course you are a cartographer, becomes the catalyst for murder. But it is not the map they are after, rather it is the information on the map that leads to the crime. Perhaps Sherlock can finally get Joan to agree to a treasure hunt after all!

‘Terra Pericolosa’ Stills

Mamie Gummer guest stars as wealthy New York heiress, Margaret Bray.

‘Terra Pericolosa’ Synopsis

“Holmes and Watson search for a thief who committed murder to steal a rare map. Meanwhile, Watson becomes concerned with Sherlock’s escalating interference into Kitty’s burgeoning personal life.”

Sherlock and Joan, three years in, still find problems in their respect for personal boundaries. We saw how well his tailing of Joan went in the early days of their partnership (recall he slept with her friend), but it is no surprise that he would resist interfering in Kitty’s life.

Last week, Kitty made a comment about her “nonexistent” friends in regards to whom she would disclose information about her work with Sherlock. Perhaps after a few good shocks from Clyde, Kitty realized she should make an effort to have a life outside of the brownstone. At least for a few hours per week.

Another change in Sherlock’s life may be the catalyst to his undoing. In an interview snippet from earlier in the week, creator Rob Doherty confirms that Sherlock will stop attending his support group meetings. In past episodes, Sherlock off-handedly mentions that he owes a great deal to those group sessions, as dull and repetitive as they may be, to keeping him sober. It all may be another test, much like the heroin in his pocket was at the close of last season, but this time he will at least have Joan on hand in case things do not pan out as planned.

Tune in to Elementary season 3, episode 6, “Terra Pericolosa,” Thursday, December 4 at 10:00 p.m. ET on CBS.