The Miss Fisher's Murder Mysteries' cold open begins with a lady dunking her paintbrushes in water as she finishes work for the day. She starts up a music box to keep her bird company as she gets ready to leave. But the bird dies, and then she does too. The next morning, Dot is full of news of the woman's death. She was Marcella Lavender (Heather Bolton), the editor-in-chief at the Women's Choice Magazine, and the writer behind the serial Blue Fairies, starring Marvin the Malevolent Monitor Lizard. (Dot is a fan.) Lavender was Miss Fisher's teacher at school, as was the assistant editor, Georgina Charlesworth (Deborah Kennedy), so she heads over to give her condolences.
Charlesworth: (Approvingly) You're a shameless opportunist.
At the magazine's headquarters, she walks in on an extensive crime scene. There's not just a body, the window's broken, and "BITCH" was left scrawled on the wall. Collins and Robinson are on site, trying to keep the murder scene clear. Charlesworth and Fisher head to the breakroom, where Miss Lavender's coworkers are catty over her passing. They are Helen Opie (Roz Hammond), the food editor, Letitia Prout (Anna McGahan), fashion and social editor, and John Bell (Peter Stefanou), the token male, writes about gardening under a women's pseudonym, though he's an Italian charmer whose real name is Giovanni. Steven (Jim Russell), the facilities manager who found the body, is Helen's husband. He says he found Miss Lavender in the morning when he came to fix the pipes, and let himself in with the master key.
Charlesworth is doing what so many women's publications do to make ends meet, publishing gossip, recipes, and the popular advice column, "Ask Artemis," to support stories on family planning and progressive values. Charlesworth needs to get into Lavender's office to get Blue Fairies for the printer, but so far has failed. Fisher flirts her way in, convincing Robinson to hand it over as soon as it's not evidence before heading home. True to his ord, Robinson stops by with it, and the news Lavender was poisoned with cyanide. He wants to ask Fisher about her former teachers, but Lin Chung interrupts. His engagement is off! Granny Lin insisted on proving the fiancée, Camellia, is a virgin. Miss Fisher is surprised to learn the girl refused, but also impressed.
Back at the crime scene, there are too many suspects. Jack learns Lavender rejected Miss Prout's pitches, like her "Migrants of Melbourne" idea and then tried to fire her for freelancing. Charlesworth inherited the magazine on Lavender's death, and her photography is a style done with potassium ferricyanide. Meanwhile, Helen says she left at six, but her husband says she got home a little after seven. (They live about five minutes from the office.) Her flirtation with John Bell may explain that time discrepancy, his alibi is he booked a hotel with a lady for the evening.
Bell is a handyman around the office as well as a writer; he fixed Miss Lavender's music box recently. But Lavender was also Artemis the Agony Aunt, and might have pissed off an outside party with her advice. Fisher takes the unpublished and never-to-be-answered letters to Dot to wade through. She turns up one letter in particular from an upset husband. Collins agrees to join in following this lead, hoping for an Agony Aunt Answer of his own if she's his girl or not.
Miss Prout repitches her "Migrants of Melbourne" article, and Charlesworth accepts it. But when Prout finds the file in Lavender's desk, there's a photo missing. Her source brings a new one, causing some last-minute fact checks. As Miss Fisher hangs out in the office, she sees Prout type something suspicious before leaving. Fisher grabs the typewriter ink ribbon hoping to check it over later. But when Lin doesn't come for dinner and Jack shows up instead, the two discover the ribbon contains a blackmail note. Fearing for Prout's safety, they race to the magazine but arrive too late. Prout's dead: shoved down the stairs. Fisher wonders if the source was involved, especially when the migrant story draft is gone.
Lin turns up with Camellia, hoping Phryne can protect her from Granny Lin. Camellia supposedly can't understand English, but there are communist writings tucked in her trunk, and she reads the Artemis letters. She admits to Phryne she's the widow of a communist hero, executed in Shanghai. She cannot go home; her father will kill her. Fisher encourages Lin to go through with the marriage; Camellia would make a strong and smart wife. When Granny Lin attempts to ship her to China, Lin decides Fisher is right. He declares the wedding back on.
Dot finally finds the original letter that set the hsuband off. The writer was suffering from postpartum depression, and Artemis gave awful "buck up" advice. The wife killed herself, the kids were taken by Welfare, and in his grief, the husband, Robert Greene (Frank Magree), vandalized the magazine offices. But he came late at night, after Lavender was already dead. Robinson is convinced Charlesworth did it, who throws up her hands at being accused, accidentally knocking over the paint water from the cold open. But there shouldn't have been water if Opie didn't fix the pipes until the next morning. The man admits he repaired the pipes the night before, accidentally catching out his wife in the lie about when she left. Helen admits she was the woman Bell met at the hotel.
Anxious to clear Charlesworth, Fisher tracks down the migrant story source, a barber named Franco (Anton Berezin). The photographs were from his time in the war. But there's a familiar figure in them, the reason Prout ran down to fact check, and which Lavender had spotted in the original photo: Giovanni Campana, which translates from Italian to John Bell. Bell was a traitor spying for Germany, and still wanted in Europe. He "fixed" the music box to eject cyanide and pushed Prout down the stairs trying to keep his secret.
With Bell arrested, and Charlesworth still needing content, Camellia becomes the new subject of "Migrants of Melbourne," proudly embracing her history. Dot fills in as Artemis but turns down taking it on full time. And Jack seems quite pleased to learn Lin Chung is engaged, leaving Miss Fisher is now free for dinner more nights a week.