Miss Fisher's Murder Mysteries usually starts with a cold open, but an embalming tool up the nose of a man to pull out his brain while still alive is extreme. But these are extreme times, as Phryne is unable to calm down after Foyle gaining entry into her home at the end of the previous episode. The house is in an uproar Cec and Bert have one clue Foyle left in their cab. It's an Egyptian-themed card for "Albert's Antiques & Curiosities," located where Foyle's old antique shop used to be.
Miss Fisher: My sins are too many and varied to mention, and frankly, I intend to continue sinning, so I won't waste your time.
The shop is where we saw the man murdered at the top of the episode. He was proprietor Albert Monkton; Fisher recognizes him as one of the defense witnesses at Foyle's trial. Foyle broke into a cabinet too and left a photo tacked up in the backroom with the murder weapon. It features Foyle, Albert, and three others at an archeological dig. Once home, Fisher sends Bert to accompany Dot to see if they can figure out what Foyle stole. For once, Fisher's keeping the photo and murder weapon from Jack is being repaid in kind. This is the second death through the nose Robinson's seen this week.
The coroner isn't pleased to learn he has to check if there's still a brain in Albert's head when Fisher produces the embalming tool as the murder weapon. There is not. Robinson asks about the other victim, who turns out to be brainless too. Both have mysterious stones embedded in their noses. Fisher recognizes the other victim, James Waters, as one of the men in the photo. At the antique shop, Dot and Bert find an empty container that's missing a silver ring, with a note indicating it was sent home from Egypt in 1915.
Fisher takes the stones found in both victims' noses to have the hieroglyphics translated at Foyle's old university by the head of the department, Professor Henry Rhodes (Matt Day). He also is one of the men in the photo and freezes when Fisher tells him Foyle is out of jail. Rhodes says the picture is from their trip to Giza in 1915. He's not in touch with Waters but does sometimes talk to Albert. The last person in the photo, a woman with dark wavy hair, he identifies as Theresa Cavalli (Nicole Nabout).
Robinson goes back through the Foyle case, hoping something shakes out. That includes bringing in Myrtle Hill (Cassandra Magrath), his kidnapping victim who escaped, and whose testimony put him away. Her story, like Janey's, involves the carnival. Foyle enticed her with tickets for her birthday, and afterward took her back to his shop. There, he drugged her with ginger wine, telling her she was one of the "chosen ones." She woke up in a church, rescued by a woman with dark wavy hair. Jack notes she says "chosen ones," and has Collins dig for other unsolved missing girls reported at the time. It turns out there were two.
Phryne shows Hill the photo, and she says Theresa is the same woman who rescued her, as Dot locates the church where Hill woke up. The priest, Father O'Leary (Dennis Coard), says someone called claiming to be Cavalli's brother, looking for her, but he claimed not to know. In reality, Cavalli joined the nunnery across the street, where Fisher and Dot find her. Cavalli says the five of them found King Memses' tomb. But Foyle had them reseal it, taking a pair of goblets, the ones from which Myrtle drank. Albert took the ring and mailed it home. Foyle became convinced his finding the tomb was preordained, and he was Memses reborn. All he needed was "four goddesses on earth" to travel to the underworld.
Cavalli accidentally witnessed Foyle drug Hill. She rescued the girl and alerted the police (though not in time to save Janey), and took her troubled soul to god. But Foyle didn't steal the missing ring; Theresa did when Albert told her about it. She hands it over to Fisher as someone watches from the shadows. Rhodes identifies the ring as Memes' cartouch, affirming his ascension into the afterlife. The stones' hieroglyphs read: "to dedicate the daughter." Seized with fear, Fisher calls home, but there's no answer. Leaving the ring behind, she runs home to find the household drugged, and Jane is gone. As Fisher panics, Father O'Leary calls. Theresa's body has been left at the altar, her brain removed.
Robinson's turning up the other girls Foyle murdered reveals all we born on Dec. 21, Memses birthday, same as Foyle. All had this birthday save one: Janey. Dec. 21 is Phryne's birthday. (It is jarring to hear them refer to this as "midsummer's eve.") As Phryne said in the premiere, it was her that Foyle meant to abduct. She's his "fourth goddess." Phryne decides to turn herself into Foyle to save Jane. In response, Robinson arrests her to keep her safe. Dot has to hold Hugh at gunpoint to get him to let Fisher go. (Ok, fine, Collins coaches her through holding him at gunpoint so he can have an excuse to unlock the cell since he can't bear to watch her cry. It's the literal best.)
Robinson goes to see Rhodes and retrieve the ring, warning Rhodes he's Foyle's next victim. But Rhodes has secretly been helping Foyle, and he has the goblets. Rhodes leads Robinson to the basement, where Foyle is waiting to knock him out. Fisher tracks Foyle down and offers herself up if he lets Jack and Jane go. Rhodes admits if he allows Foyle to do this, the old nutter will kill himself, and it will all go away. Before killing her, Foyle confesses he did kill Janey and tells Phryne where the bodies are buried. Meanwhile, Robinson wakes and breaks out of the tomb where he and Jane are trapped. Fisher drinks the poison, but not before manipulating Rhodes and Foyle to fight over who goes to the afterlife last.
In their fight, Foyle is shot, though not fatally. Jack bursts in, in time to save Fisher from the poison. Foyle's confession, and the bodies being found, means he'll be tried for all four murders and be hanged. Fisher gets to say goodbye to her sister properly, as Aunt Prudence arranges a funeral. As the season ends, Phryne throws a midsummer birthday party to celebrate the memory of Jane and the whole cast dances and drinks champaign.