Cabot Cove episodes average five per season in this series, and, on occasion, the action transports into the interior of Maine.
The primary setting of "Unfinished Business" lies beyond Cabot Cove County and, therefore, the jurisdiction of its Sheriff, yielding the way for other law enforcement officers to interrogate suspects.
It all begins ten years earlier than the present day at the backwoods Juniper Lake, a once-promising resort, at which a group of investors is swindled in a Real Estate scheme, leading to the demise of Dectective Lowel Dixon.
And now, on the night of his third retirement banquet, Lieutenant Detective Barney Kale (Pat Hingle) vows justice for the murder of his former partner, with a vow to return to Juniper Lake for one final investigation.
News of Barney Kale's announcement makes headlines across the state. Dr. Terence Mayhew (Lloyd Bochner), while skeet shooting, reads this report, thus causing him to cancel his forthcoming flight to Tokyo.
Entrepreneur Cynthia Tate (Hayley Mills), former secretary to the investment group, receives a call from Detective Kale at her unlisted number, alerting her of his plans to renew the investigation.
Dr. Seth Hazlitt (William Windom) clips the newspaper article to slide into his desk drawer, as Jessica Fletcher (Angela Lansbury) visits his office. He then explains about his losses to the failed investment scheme after the passing of Ruth.
Juniper Lake Resort proprietor Jake Sanford (Don DeFore) rents a cabin to a young couple, Maggie Roberts (Erin Moran) and Gary Roberts (Erich Anderson), before he welcomes Cynthia Tate, who enters upon their exiting. "Do you mean that you haven't heard, Jake?" she asks, then filling him in on Barney Kale's plans to reopen the case of Lowell Dixon.
Later that evening, Jessica receives a call from Cabot Cove Sheriff Amos Tupper (Tom Bosley), who inquires to the whereabouts of Seth. "Amos, can you drive over here right away? I'll explain everything along the way," she tells him.
Upon their arrival at Juniper Lake Resort, Jessica and Amos encounter a screaming Maggie Roberts, who has just discovered a body in a cabin. (Tom Bosley and Erin Moran had played father and daughter on the series "Happy Days" for many years, but here they have no familiarity with each other, as their scenes are carefully framed to guide viewers beyond their famous co-starring roles.)
When Sheriff McCoy (J.D. Cannon) arrives the next morning with First Deputy (Phillip Clark) and Second Deputy (James Bartz), they escort a handcuffed Seth Hazlitt from their vehicle, as a prime suspect to murder.
Under his jurisdiction, Sheriff McCoy examines evidence of Dr. Terence Mayhew's missing rifle, a page containing Cynthia Tate's unlisted telephone number, and Seth's roaming the woods, while Jessica conducts a more clever investigation of her own.
