This week's Miss Fisher's Murder Mysteries starts with a dying man locked inside a mysterious room as photographs burn before cutting to Phryne and Dot on the road to see about a new case at Voigt's Winery. It's the day of the town's wine festival, Sergeant Clem Ford (David Field) points the way. They head over just in time to catch Erik Voigt (James Saunders) make a speech, namechecking his right-hand man, Frank Ford (Luke Clayson).
As Phryne takes in the scene, Dr. Bob Ryan (Geoff Morrell) steps up to hand her a glass. But their introductions are cut short when his daughter, Flora (Ramona Von Pusch), Frank's wife, comes running up, screaming about a body.
Jack: What kind of town is this?
Fisher: They make very good wine.
The dead man is Erik's brother Oskar, who hired Miss Fisher, but Sgt. Ford turns on her with alacrity when she tries to help. Phryne decides she owes it to Oskar to look into his death as she and Dot check in to their hotel with owner Valma Brightwell (Geneviève Picot). But the phone rings, and suddenly there's no room at the inn. Fisher forces the issue with money, but her presence is unwelcome. She finds Dr. Ryan, the hotel's other lodger, comforting Flora, who is genuinely heartbroken over Oskar's death. Flora was the Voigt's housekeeper and the last to see him alive. In her grief, she babbles on how the brothers didn't get on. Ryan tells Fisher Oskar died of heart attack, like his father, Mikael, who passed in 1918.
Fisher eyes him suspiciously, wondering aloud about the bruising on Oskar's head. Ryan is flustered; as he leaves, Sgt. Ford threatens Fisher to leave town. Erik doesn't want her here either, insisting Oskar hired her to stop Erik from giving half his share of the farm to Frank. Oskar and their mother abandoned the farm, Erik and Frank do all the work. Oskar only turned up when Erik asked permission to cut in Frank. (Frank supposedly doesn't care, it's his father, Sgt. Ford, who pushed for it.) Fisher counters she was hired because Oskar had photographs that proved a "suspicious death," nothing to do with Frank or the farm. Erik seems genuinely taken aback.
When the hotel puts a snake in her room, she heads downstairs and calls Jack. With Ford and Ryan in the main room, she codedly talks about her car breaking down. Collins turns up Voigt's death report, and Jack begins investigating with a call to Ida (Kerry Walker) Oskar and Erik's mother. Meanwhile, Erik catches Fisher investigating the storage house; she shows him the evidence Voigt was killed inside a vat, convincing him to hire her. She also finds photograph negatives, a German poetry book missing pages, and a letter to the Bendigo Standard asking for archival photos of the 1918 festival. Erik says there was no 1918 festival since Mikael died the day before. Back at the hotel, Fisher's pistol has disappeared from her room.
The next morning, Ford attempts to take Oskar's body away. Thankfully, that's when Jack and Collins show up. Ford tries to go "copper to copper," claiming Fisher is making stuff up, only to find himself having to account for his whereabouts at the time of Frank's death. He says he was out of town, and the bridge was out, delaying his return, which Fisher can confirm, she saw him drive up when he gave her directions to the festival. Frank confirms to Jack the burnt sulfur Fisher found in the vat would have given off fatal fumes, had Oskar been trapped inside.
With Jack now on the case, Ryan admits his "heart attack" write up might have been "hasty," but insists Sgt. Ford didn't pressure him. But Erik disputes Ryan's claim his father died of a heart attack. The family never saw the body; the coffin was nailed shut. He believes his father committed suicide due to being locked up for years during the war for his German heritage. It's why he's contesting Mikael's will, which insists the farm much be family-owned. As they walk through the vineyard, a shot is taken at Erik, hitting Jack's hat instead, and it seems it came from Fisher's missing gun.
Collins takes Dot out for a walk with plans to propose using a Shakespeare speech, but Dot sees Flora acting odd around the vineyard's scarecrow and hurries after her. The scarecrow has a German love poem in it, the missing page from Oskar's book. Flora admits they were having an affair; Frank knew too, but he figured it would pass. Erik runs up to Jack and Phryne, saying Oskar's body has disappeared and Sgt. Ford with it. Moreover, Ford's map of the area shows his alibi is bupkis; there is a shortcut back to town around the bridge. When Sgt Ford returns, Jack locks him up for obstruction.
Meanwhile, Dot has the negatives reprinted and shows them to Ida. It turns out they're from that "1918 Festival" everyone claimed never happened, and Mikael is in them, shaking hands with Dr. Ryan. But when Fisher and Jack confront Ryan, Valma pulls Fisher's gun out of her laundry, and takes the jail keys from Jack, telling Ryan to let Ford out. But when Ford sees Valma holding the two at gunpoint, he puts her under arrest.
All three then confess to how Mikael died. Valma learned her son was dead the morning of the festival, and went mad with grief. After the staged photos with the paper, they discovered she had written "Dirty Kraut" on the town hall wall, and as Mikael washed it off, she came in and shot him in a rage because his sons survived, while she lost both her husband and her son. The town covered it up with a suicide whisper campaign since they knew the family wouldn't believe the heart attack story. When Oskar realized the truth, Ryan murdered him to protect Valma (his son also died in the war) and burned the photos. Erik is heartbroken when he learns the truth, but at least he and his mother have a touching reunion.
Meanwhile, Phryne has caught on to why Collins and Jack were talking Shakespeare earlier. As she gives Jack a new hat, Collins shows up in the kitchens as a surprise for Dot. His Shakespeare recitation is not great, but she doesn't care, and neither do the rest of us. There's going to be a Miss Fisher wedding episode!