Attending a dinner party hosted by Sarah’s friend Fiona Matthews celebrating the success of a new app she invented, things take a dire turn when Fiona is poisoned and a storm strands everyone in the mansion, and it’s up to Charlie and Rex to find the culprit while Sarah fights to keep her alive, all the while bringing secrets about the guests to light. Meanwhile, while helping with the investigation from the station, Jesse finds an unlikely partner for an online horror movie trivia game in Superintendent Donovan.
Tropes:
- Accidental Murder: Grace came to the mansion looking for Sarah only to run into Jamie, who quickly deduced that Grace was not one of the guests and went to call the police. This led to Grace knocking Jamie out with a shovel, only for Jamie’s diabetic condition making her weak enough to make the hit a fatal blow. Afterwards, Grace scrambled to put Jamie’s body in the latter’s car and drive off before anyone noticed, but instead decided to assume her identity to infiltrate the dinner party using Jamie’s notary stamp and emergency number bracelet, stashing Jamie's body in the shed and throwing her wallet into the trees.
- A Simple Plan: Grace came to the mansion with the intent to kill Sarah as revenge for what happened to Grace’s husband. Her plan was to somehow infiltrate the dinner party and secretly poison her with fentanyl and leave without anyone noticing her, with the notary Jamie Quinn appearing outside the mansion being a convenient opportunity. However, Grace ended up accidentally killing Jamie instead of knocking her out, her many attempts were either foiled or poisoned the wrong targets, and she gets arrested shortly after her cover is blown.
- Blatant Lies: When the real Jamie Quinn showed up to the mansion and found Grace outside peeking in through a window, Grace claimed to be one of the guests, only for to Jamie to not believe her and asked Grace to prove it by telling her the name of the host. Grace was unable to answer, which led to Jamie calling the police and Grace accidentally killing her trying to knock her out.
- Childhood Friends: Fiona is one of Sarah’s best and oldest friends, and Sarah is not pleased that someone tried to kill her. Even more so when she finds out that Russel is cheating on Fiona with Laura.
- Closed Circle: The party guests consist of Charlie, Rex, Sarah, Fiona’s husband Russel, Tori Hawley and Dean Cody (Fiona's former colleagues at the software company she used to work at), Laura Benante (a friend Fiona and Russel met at a wine making class), and the notary Jamie Quinn. Except "Jamie Quinn" is actually an uninvited guest, Grace Buckley. The partygoers are all stuck at the mansion due to the storm surge washing out the roads, but fortunately things eventually get better and they're able to leave.
- Dead Person Impersonation: The real Jamie Quinn is dead. The woman both responsible for her death and impersonating her is Grace Buckley, who is seeking revenge on Sarah for the role she played in the conviction of Grace's husband Vince.
- Detrimental Determination: As Grace herself admits, it would've been a better idea to just cut her losses and drive off in Jamie's car with the latter's body while nobody noticed and save killing Sarah for another day. Instead, she decided to infiltrate the dinner party using Jamie's notary stamp and diabetic bracelet which led to her digging herself into an even deeper hole by hurting multiple people with her botched murder attempts before finally being exposed and arrested.
- Foreshadowing: When Fiona manages to briefly regain consciousness, Charlie and Sarah ask who it was that poisoned her, assuming that it was Russel. She responds "No, Tori" before falling unconscious again, which prompts Charlie to interrogate Tori. Fiona was actually trying to say "notary", which leads to the revelation that the Jamie Quinn the group had been interacting with is an impostor.
- Freudian Excuse Is No Excuse: Grace is out to avenge her husband who was murdered in prison, going after Sarah because she was the one who performed the DNA lifting technique that made his arrest possible. While Charlie offers his sympathies about what happened to Vince, he points out that it does not excuse Grace from the fact that she killed and hurt innocent people who had nothing to do with her revenge crusade, even if it was all unintentional.
- From Bad to Worse: Things only get worse when Fiona's condition worsens to the point that she needs to go to the hospital and the body of an unknown woman is found outside in the shed. The unknown woman is the real Jamie Quinn, who was killed by Grace.
- Happily Married:
- Fiona and Russel, with Russel having to constantly tell people that he married her for love, not her money. Turns out he’s been having an affair with Laura behind Fiona’s back, claiming it to have been a case of weakness and stupidity due to Fiona being rarely home because of her working on her app and that he still loves her. Sarah doesn't buy it for a second, and Fiona is angry enough to decide to file for a divorce when she finds out.
- Grace makes it clear that she and her husband Vince loved each other very much, and his conviction and eventual death in prison hit her hard enough to want to seek revenge on those she deems responsible.
- Hidden Depths: Donovan is apparently a vintage horror movie buff, although he prefers to keep this fact about himself a secret.
- Moral Myopia: Grace bears a grudge against Sarah because of the role she played in the conviction of Grace’s husband Vince, despite Grace being aware that he was a drug trafficker whose sentence was earned after he chose to be uncooperative with the police as Charlie points out.
- Never My Fault: Or rather "Never My Husband's Fault". Grace blames Sarah for Vince’s conviction because she was the one who performed the DNA lifting technique that made his arrest possible. Charlie however fires back that Sarah was just doing her job and that Vince was a criminal and that what happened to him came about from the choices he made, only for Grace to retort that it's unlikely that her husband made the choice to let himself get stabbed to death in a prison cafeteria.
- Notary Nonsense: Grace infiltrates Fiona's dinner party to murder Sarah by using the notary stamp she took from the notary in attendance, Jamie, whom Grace accidentally murdered after she caught her trying to sneak in. Notary stamps are a tool of the trade, but using one as a form of ID definitely qualifies as nonsense.
- Obfuscating Disability: Grace was only faking being diabetic as part of her disguise as the real Jamie Quinn, being able to sell it better due to her knowledge of the symptoms from taking care of her late husband who also had it.
- Recovered Addict: Dean has a past criminal record of drug possession charges and was inspired by Fiona to go to rehab. Turns out he relapsed almost immediately after he was released and didn’t want Fiona to find out as she had believed in him so much. Fortunately, he has a stash of naloxone in the trunk of his car to help Fiona when she starts overdosing again.
- Revenge: A year prior to the events of the episode a man named Vince Buckley was arrested for trafficking heroin and fentanyl, with the prosecutor giving him a huge sentence trying to get him to flip on his supplier. When Vince was murdered in prison the night before the dinner party, his wife Grace sought revenge on the people responsible for her husband's conviction, targeting Sarah because she was the one who performed the DNA lifting technique that made the arrest possible.
- Spanner in the Works: Grace’s plan was to simply poison Sarah’s drink and leave quickly, only for things to go sideways when Fiona drank the poison instead, mistaking Sarah’s glass for hers. Things only got worse for Grace when the storm ends up stranding her in the mansion with the other guests and she's unable to leave without Charlie stopping her, leading to her being outed as the one behind everything.
- Tampering with Food and Drink: Fiona is poisoned by wine spiked with fentanyl and is left in a critical condition while Sarah does everything that she can to help her. A bottle of scotch that Sarah and Russel were going to drink from turns out to have also been poisoned, but luckily Rex managed to figure it out before either of them drank it. Grace’s plan to kill Sarah involved poisoning her glass of wine with fentanyl and then leaving quickly before anything happened. When Fiona ended up drinking it instead, Grace resorted to spiking the scotch as a backup plan, only for it to fail as well due to Rex detecting the poison.
