On his way back from a late-night dinner, Reverend Robin Sage dies from acute food poisoning. The woman he had dined with, Juliet Spence, is also sick but suffers nothing worse than severe vomiting. It turns out that the Reverend had consumed water hemlock as part of his dinner - a deadly poison, which nonetheless does not cause vomiting. It seems that Juliet Spence spiked the dinner with hemlock and then took an emetic herself. But then, why would she want to kill a harmless clergyman? And was Reverend Sage even the intended victim?
As Lynley and Havers investigate, it seems more and more likely that someone else is behind the poisoning. It could be Steve, the local constable, who is in love with Juliet and might have been jealous of her closeness with the Reverend. It could be Juliet's daughter, Maggie, who resented her mother's affection for Steve and thought that Steve was going to be the dinner guest. Or it could be Polly Yarkin, Steve's jilted lover, who desperately wants to win Steve back from Juliet. And somehow, linked with all of this, are specters from Reverend Sage's past - his dead child Joseph, and his wife who committed suicide.
Meanwhile, Lynley and Havers navigate the first major hazard of their personal relationship, with surprising consequences.
- Arson, Murder, and Jaywalking: When Lynley has Havers' flat repainted without telling her, Havers calls out Lynley on interfering with her life, of patronising her and being a fascist. Then: "I don't even like duck white."
- Brooding Boy, Gentle Girl: Inverted in the Lynley-Helen relationship. Helen, as played by Lesley Vickerage, is far more dark and depressed than Lynley.
- Dude, Not Funny!: In universe, Tony the coroner's remarks were way out of line. Lynley's offer to Havers to bring him up on unbecoming conduct charges was genuinely justified.
- Cut Himself Shaving: Polly Yarkin uses the "fell down some stairs" variant when Lynley and Havers see the injuries sustained from Steve beating up on her. They see through it immediately.
- Department of Child Disservices: Whether intentionally or not, Reverend Sage's sister-in-law seems to be running one.
- Disappeared Dad: Maggie's father isn't around, and it's implied he's deceased. Turns out he never existed, and the closest thing she had to a father was, ironically, Vicar Sage, who was her mother's husband.
- Everyone Is a Suspect: Part of the difficulty for Lynley and Havers in the case is that virtually everyone they encounter has a reason to want Juliet and/or Vicar Sage dead and they have to figure who the actual target was and who might have just been collateral damage.
- Faking the Dead: Mrs. Sage, aka Juliet, who supposedly committed suicide by jumping off a ferry headed to France, but in fact fled to France for a time before coming back to Britain, kidnapping Maggie from her biological mother and starting her life over. Vicar Sage's death was apparently the result of him finding this out.
- Friendship Moment: Despite her issues with Lynley in this episode, Barbara thinks enough of him to call him a "clever, considerate man" when a particularly vile copper starts slinging insults at him.
- Green-Eyed Monster: Polly Yarkin is quite obviously jealous of Steve and Juliet's relationship. Steve also accuses her of hastening his own wife's death while she was dying of cancer, though we never get confirmation that she actually did this.
- It's Not You, It's Me: Helen's reason for deciding she and Lynley are Better as Friends after their one-night stand.
- Love Potion: The reason Polly Yarkin has a book on herbs.
- Mama Bear: Juliet Spence would do anything to protect Maggie. But then, of course she is not really Maggie's mama.
- Murder the Hypotenuse: The possible motive of both Steve and Polly Yarkin in the poisoning. Steve also accuses Polly of hastening his own wife's death when she was dying of cancer, though it's never confirmed if this actually happened.
- Never Trust a Title: Honestly, why missing Joseph? The one who's really missing is Mrs. Sage. Might be construed as Mrs. Sage being the one missing her deceased son Joseph, which prompts her other actions.
- Parent with New Paramour: The reason why Maggie Spence hates Constable Steve.
- Quirky Curls: Polly Yarkin, though of the darker variety in terms of her "quirks", being obsessed with Steve to the point of owning a book on herbs to try and make a Love Potion for him.
- Rant-Inducing Slight: Lynley's having Havers' flat re-painted without telling her. She doesn't spare any punches, including accusing Lynley of behaving like "the earl patronising the peasants."
- Really Gets Around: Steve seems to be doing pretty well in the small social circle of the Lancashire village.
- Red Herring: Polly Yarkin is set up as incredibly suspicious from the first scene, including having a book on herbs, but she's not the killer (of the Vicar, at least).
- Side Bet: The verdict at Scotland Yard was that there was no way Lynley and Havers' partnership would last more than a month. Alas for them, despite a few hiccups, they're still partners seven years later.
- Teen Pregnancy: Maggie's birth mother was in her teens when she had her, which is why Juliet thought she could take her and no one would notice.
- Yandere: Polly Yarkin for Steve. The very first scene has her spying on Juliet's house to see if Steve comes by, and she's seen doing it again later. Doesn't mean she's the killer.
- You Fail Pharmacology Forever: Lynley and Havers find it incredibly unlikely that Juliet would mistake wild parsnip for water hemlock considering she's a trained herbalist and conclude someone else must have slipped it into the food which turns out to be wrong, since Juliet knowingly put it in and induced vomiting in herself.
- You're Not My Father: Maggie Spence uses almost this exact line to rebuff Steve's attempts at kindness.