A masked burglar breaks into Lo's London flat and traps her inside her locked bedroom.

Waking from a nightmare at Judah's apartment, Lo strikes him with a lamp, splitting his lip.

Lo boards the luxury cruise ship Aurora Borealis and meets the assembled guests for the first time.

Lo knocks on the door of Cabin 10 and borrows mascara from a guarded and reluctant young woman.

Lo wakes in the night to what sounds like a woman's scream followed by a heavy splash.

Nilsson investigates Cabin 10 and declares the room has been unoccupied for the entire voyage.

Lo returns to her cabin and discovers the mascara borrowed from the Cabin 10 woman has vanished.

After a spa mud wrap, Lo finds the threatening message 'STOP DIGGING' written in steam on a mirror.

Lo spots the woman from Cabin 10 alive and working as a waitress in Cole Lederer's photographs.

Lured into the lower decks by the Cabin 10 woman, Lo is knocked unconscious and locked in a cell.

Lo's captor accidentally removes a painted-on eyebrow while washing her face, revealing a bald, gaunt skull beneath.

Carrie confesses she is Bullmer's mistress and has been impersonating his dead wife Anne for the entire cruise.

Carrie swaps clothes with Lo and sends her out disguised, giving Lo a chance to flee the ship.

While climbing the glass barrier on Bullmer's veranda to escape, Lo slips and falls into the freezing fjords.

Farmer Konrad Horst rescues Lo from the wilderness; police confirm two bodies have been pulled from the sea.

The story begins when Lo is traumatized by a home invasion that leaves her sleepless and shaken, then sent off on a luxury cruise assignment aboard the Aurora Borealis. Her first night at sea, she witnesses what she believes is a murder, but every piece of evidence vanishes and the ship's staff dismisses her as unstable. As threats escalate against her, Lo is finally lured below decks, knocked out, and imprisoned in a cell near the engine room. Her captor turns out to be the woman she thought was dead, who is hiding a far more elaborate secret about the ship's owner and his dying wife. A fragile bond forms between the two women, leading to a desperate escape attempt and a terrifying plunge into the Norwegian fjords before Lo finally reaches safety.

The core mystery of a body overboard on a luxury cruise.

Still bleeding from the burglary, Lo uses a nail file to chisel the doorknob off and escape her bedroom.

Lo and Judah argue about the relationship's future; Lo slams the door and leaves for her train.

On the train to the port, Lo reads about Lord Bullmer's rise from homelessness to billionaire in her press kit.

Lo attends Lord Bullmer's welcome presentation in the Aurora's lavishly decorated all-white lounge.

A drunken Ben Howard corners Lo in the hallway outside their cabins and grabs her breast.

Nilsson takes Lo on a tour of the lower decks to identify the Cabin 10 woman among the staff.

Nilsson reveals Ben disclosed Lo's antidepressant use and drinking history; Lo erupts in fury and throws him out.

Lo confronts Ben about betraying her, and he surprises her by saying he believes her account of the murder.

Steward Karla nervously hints to Lo that a crew member may have smuggled a guest secretly aboard the ship.

On deck, Tina offers Lo a freelance contract, which Lo declines due to a non-compete clause at Velocity.

During a bridge tour, Ben spots a contact named Jessica on Archer Fenlan's phone matching Lo's description of the Cabin 10 woman.

Lo meets Lord Bullmer alone in the dining room and walks him through every detail of what she witnessed.

Imprisoned below decks without her medication, Lo has a vivid nightmare of the Cabin 10 woman shedding her skin and hair.

After Lo nearly faints from hunger, Carrie returns with food and finally reveals her own name.

Searching Bullmer's cabin for Anne's wallet, Lo discovers a handgun hidden beneath scarves in a dresser drawer.

In the immediate aftermath of the burglary, Lo fights her way free of her own bedroom and refuses to abandon her career opportunity despite the trauma. Aboard the Aurora, she encounters a cast of suspicious guests and staff while a drunken assault by former boyfriend Ben Howard complicates her ability to trust anyone around her. As her investigation deepens, clues accumulate — a hinted smuggled passenger, a matching name on a stranger's phone — even as authorities use her mental health history to shut her down. Imprisoned in the hull without her medication, Lo endures terrifying nightmares before Carrie finally breaks down and begins to bond with her. Lo's escape route through Bullmer's cabin reveals a hidden weapon and ends in a desperate gamble into the dark Norwegian sea.

The investigation, the suspects, and the clues aboard the Aurora.

After the burglary, Lo tries to take a bath to calm down and suffers her first traumatic flashback.

After a hospital visit for his injuries, Judah reveals he turned down a dream job in New York to stay with Lo.

Lo's bathroom door slams shut while she showers alone on the Aurora, sending her into a panic.

At the first dinner, Lo notices Anne Bullmer wearing a headscarf and looking pale and gravely ill.

Lo returns to her cabin after dinner and is disturbed to find the staff have unpacked all her luggage.

Desperate not to investigate alone, Lo decides to tell Ben Howard everything she witnessed about the murder.

Cole Lederer cuts his hand at the hot tub and his camera falls in the water, destroying all photos.

Lo blows steam on her bathroom mirror and defiantly writes 'NO' in response to the threats being made against her.

Owen White tells Lo that the canceled guest Solberg also suffered a mysterious break-in shortly before the cruise.

Lo discovers her phone has been stolen and finds a wet footprint near her cabin's unlocked veranda door.

Lo breaks a plastic food tray into jagged pieces and attacks the Cabin 10 woman at the door, but is overpowered.

Lo convinces Carrie that Richard Bullmer intends to kill them both to cover up Anne's death.

Locked in her cell, Lo hears the gangplank lower and realizes the guests are departing the ship without her.

A Norwegian hotel manager calls someone named Richard on the phone; Lo realizes she is in danger and flees into the dark.

A large Swiss bank transfer arrives for Lo carrying only the message 'Tiggers bounce,' suggesting Carrie is alive and free.

Lo's trauma begins not at sea but in her London flat, where a burglary triggers a PTSD flashback and a sleepless unraveling that will follow her onto the Aurora. Small, unsettling discoveries aboard the ship — a cleaned room, a cancelled guest's stolen passport, a destroyed camera — build into a picture of deliberate conspiracy. Every choice Lo makes about whom to trust brings new danger, as evidence vanishes and even well-meaning allies become suspect. Deep in her cell, Lo makes the pivotal decision to push Carrie hard enough to break through her loyalty to Bullmer, changing the course of both their fates. The novel's final revelations — that the sea victim was actually Anne Bullmer, that Richard was murdered rather than a suicide, and that Carrie has wired Lo a fortune from Switzerland — reframe the entire story and confirm both women's survival.