Last week, Annika ended with both mother and daughter diving headfirst into relationships they're keeping on the down low from one another: Annika with Morgan's former therapist, Dr. Jake, and Morgan with Annika's coworker's sister Erin. This week continues the sneaking about and charades as both have their respective significant others spend the night. In an irony worthy of the Gift of the Magi, both are so focused on keeping their secrets they are oblivious to what's being kept from them.
Michael: Is there a name for people who go at it as much as this in public?
Annika: Yeah, I believe they call them "Young."
However, Annika's crime scene lecture is not about the O'Henry classic but the Greek Dionysian festivals. These drunken orgies could quickly turn from hedonism to fighting; that happened on this party boat, where real estate developer Paul Gilbride was chucked overboard in the middle of his wedding anniversary. His wife, Gaynor (Hilary Maclean), is super drunk, but her BFF, Camela MacGowen (Anita Vettesse), tells Annika the Gibrides' neighbor, Mem Yiannopoulos (Mel Raido), whose full name, I kid you not, is Agamemnon, as in the Dionysus festival play) had an altercation with Paul earlier that evening, and was longer on the boat.
Carmela's son Gio (Cristian Ortega), the Gilbrides' godson, takes them home, while Annika and Blair head to Mem's farm. They find him drunkenly firing a shotgun, screaming how Paul screwed him over, convincing him not to put up wind turbines on his land, then stealing the deal from under him while Mem was out of the country for a funeral. But he left right after punching Paul at the party and had no idea the man was killed afterward, and CCTV confirms it.
The ship's CCTV was disabled, suggesting premeditation. The storage room is ransacked, waterlogged, with Paul's St. Christopher necklace on the floor. Paul died of a heart attack during what looks like an amateur waterboarding. Michael notes the ship had a scheduled stop just after the time of death, where Gio signed out along with caterer Veer Talwar (Bhav Joshi). Paul's office reported a break-in three days ago, so Annika and Blair ask Gaynor about it. Carmela tries to shoo them off, but Gaynor cries over Paul's necklace. She says Paul knew who broke in and didn't want them in trouble; she thinks it was ex-contractor Doug.
However, Gio attempts and fails to hide a box of money as Michael and Tyron arrive. At the station, Gio gets upset when asked why he's living at home, saying he moved back when his dad contracted cancer and died. But it's Michael calling Paul a "best friend" that sends Gio into an asthma attack, huffing Paul was no friend to them. At Paul's office, his office manager Louise (Naomi Stirrat) denies Paul knew who took the money or that he and Doug were at odds. She does note Gio met with Paul that day; Gaynor was there, trying (and failing) to change the venue. Tyrone asks for Paul's laptop; Louise says she'll unlock it, deleting files as she does.
Michael scolds Annika about keeping Dr. Jake on the DL, so when Morgan shows up at the station, Annika drags her to an interrogation room and confesses. Considering Morgan was there because Erin left her phone after spending the night, and she was handing it off to Blair, that's pretty funny. Morgan does not take the opportunity to come clean herself but does accept Jake readily (too readily for his comfort) and even teases her mom that she'll have to start cooking again.
Morgan should have 'fessed up because Blair tells Annika Erin and Morgan are dating, leading Annika to attempt to get Morgan to confess at dinner while Jake is over. Before it can get too awkward, the phone rings and Annika has to run to work as Blair tracks down Veer, who shunted the CCTV outside his flat just like the one on the boat. He saw the cops coming, so he was gone when Annika and Blair enter his room. That leaves Jake and Morgan to talk, but her treating him like he's still her therapist convinces Jake that he and Annika should move slower, lest Morgan get too attached.
Michael discovers the files Louise deleted, which chronicle Doug and Paul's dispute, where Paul refused to pay Doug for "shoddy work." Annika and Michael go to Paul's office, only to find her and Doug en flagrante. Louise staged the break-in to take the money Paul owed Doug, plus more, because "she works hard." She says Paul didn't turn her in to have something over her; however, she didn't kill him; she and Doug filmed themselves having sex on the boat at the time of his death. Meanwhile, Veer finally turns up and admits to disabling the CCTV. He's a paranoid shroomhead and does it everywhere.
Separating the CCTV from Paul's death changes things. Instead of assuming it was premeditated, it might have been an impulsive thing, or an accident, someone trying to waterboard Paul to get him to confess something, who then panicked when he died. That someone looks to be Gio. The pendant is not Paul's, as Paul's was engraved, and this one isn't. However, Paul gave one to Gio as his godson, which wasn't engraved. And yet, Gaynor claimed it was Paul's when she knew it wasn't.
Michael and Annika return to Gaynor's house and separate her from Carmela. She admits she protected Gio by pretending the necklace was her husband's. Gio comes home and admits he was angry at Paul because his father died not just of cancer but mesothelioma. For those who don't regularly watch American commercial TV and haven't seen the endless ads, mesothelioma is contracted from inhaling too much asbestos. When Paul's originally bought the boat, it was filled with the stuff. Gio and his dad renovated without Paul, who knew it was dangerous. It also causes the sufferer to feel like they are drowning in their own fluids.
Gio admits his "asthma" is cancer; he's dying too. But he didn't have the necklace; Gio threw it at Paul in the office when Paul's first response was panic that Gio would sue. Gaynor was there; it's why she tried to change the venue; knowing the boat killed one man and was killing their godson was too much. She was so angry she borrowed Carmela's scarf, took Gio's necklace, and forced Paul to wear it while she waterboarded him to make him confess he knew the boat was to blame for Gio and his father's cancer; killing him was an accident.
Gaynor then runs for it, and when Michael and Annika find her, she's on the boat doused in gasoline, setting herself on fire in hopes of blowing up the ship. Thankfully, Michael rushes her, and they go over the side into the water, putting her out. Annika heads home and tells Morgan to enjoy her time with Erin. Chastised and realizing her mom and Jake are taking it slow for her sake, Morgan invites her mom to come on their kite flying date and get to know her girlfriend.