August is almost over, which means so is “Garage Sale Mysteries” Month on Hallmark Movies & Mysteries. The last of the four newest movies in the franchise, “Garage Sale Mysteries: Murder in D Minor,” premieres Sunday night and will see Lori Loughlin’s Jennifer Shannon investigating some strange events.

“Following the death of elderly local arts patron and collector Karl Dietz (Mel Tuck), garage sale shopper extraordinaire Jennifer Shannon and her resale business partner Dani (Sarah Strange) purchase a rare, pre-WWII German piano at the auction of his expansive collection,” the movie synopsis begins. “Before the collection even goes up for auction, however, auction house proprietor Conrad Siles (Michael Ryan) and his security man Dwyer (Sean Tyson) are already angling to locate what they believe to be a hidden cache of art treasures which far surpasses the existing collection in value.”

Meanwhile, Jenn’s daughter Hannah (Eva Bourne) begins a tutoring gig, and Jason (Steve Bacic) supports his son Logan (Connor Stanhope) with his basketball team. Back at Rags to Riches, client Helen Bauer (Nicola Lipman) reveals to Jenn that one of the expensive paintings at the auction is very similar to one she remembered from when she was younger in post-war Berlin. This seemed especially worth sharing because Karl Dietz was also from Berlin.

garage sale murder d synopsis
Lori Loughlin stars in “Garage Sale Mysteries: Murder in D Minor” on Hallmark Movies & Mysteries. Crown Media / Sven Boecker

“Soon, questionable events begin happening around some of the items auctioned from the Dietz collection: one of two paintings Helen had purchased is vandalized during a home break-in; Dean Connick (Jeffrey Joseph), whom Jenn and Dani hired to restore the piano they purchased, is brutally attacked and knocked unconscious in the repair room of his shop and the back side of the piano was pried away, and a Frenchman named Jacques (Chris William Martin) begins a relentless campaign to purchase the piano from Jenn and Dani, despite their ongoing refusals to sell,” the synopsis reveals.

Jenn starts to believe that Jacques had something to do with Helen’s break-in after surveillance footage from Dean’s shop shows that he was there close to the time of the attack. If he was there for that, then he might’ve been involved in the break-in, too. To top it off, Jenn learns that Jacques won the bid for a Biedermier armoire but didn’t pay for it or collect it. She then sees Siles and Carolyn (Alison Wandzura), Dietz’s granddaughter, get into an argument because the auction happened without her knowing.

“Before long, the ‘detective’ in Jenn gets the better of her curiosity and she becomes convinced that there must be valuable treasures that Dietz had hidden away, and that several people – including Carolyn, Siles and Jacques, for starters – would like to get their hands on them, and perhaps at any cost,” the synopsis continues. “Working with Detective Lynnwood (Kevin O’Grady) with her usual ‘unofficial’ style of investigating, Jenn realizes that not only could there be a treasure trove of hidden art, but that Karl Dietz may very well have been murdered in order that someone could find it.”

Jenn starts to narrow down her suspect list, but she unknowingly alerts the killer that she’s getting close. This puts her in danger because the killer has no problem taking another life in order to get Dietz’s treasures.

Unmask the killer when “Garage Sale Mysteries: Murder in D Minor” debuts on Hallmark Movies & Mysteries on Sunday at 9 p.m. EDT.