Helen Cross is a retired British criminal barrister who prefers evidence to emotion. Susan Marsh is a retired paramedic who knows a suspicious death when she sees one. They were hoping for a relaxing holiday. They got a crime scene with a sea view. When Helen agrees to join Susan on the O&C Alora for a wedding cruise to the Caribbean, she expects nothing worse than mediocre cabaret and organised fun. She doesn't expect murder. When a wedding guest is found dead at the bottom of a staircase during a storm in the Bay of Biscay, the ship's Head of Security calls it a tragic accident. Drunk passenger. Rough seas. Case closed. Then a second guest is found dead in the spa. The ship's doctor calls it heat exhaustion. But Susan spots what the medical team missed—the evidence screams murder. Trapped in the middle of the Atlantic with a useless security team and a killer picking off wedding guests one by one, Helen and Susan must trade the sun loungers for the interview room and use every trick in their professional arsenal to uncover the truth. They have six days before the ship docks in Barbados and the killer vanishes forever. Unfortunately, the killer knows it too—and they've just decided that two inquisitive pensioners might be the next items to slip overboard. Perfect for fans of Richard Osman's The Thursday Murder Club, Robert Thorogood's The Marlow Murder Club, and the sharp wit of Deanna Raybourn.

Helen swore she'd never set foot on another cruise ship. Susan booked them on one anyway. Ten days through the Arabian Gulf. A ship full of entertainers. And a magician whose entire career rests on a trick he claims his mentor taught him before drowning forty years ago. But someone onboard knows the truth. When a member of a Frankie Valli tribute act collapses with mysterious symptoms—burning feet, hair loss, violent illness—Helen recognizes what the ship's doctors dismiss as norovirus: thallium poisoning. Straight out of Agatha Christie. Then his cabinmate dies. The ship's medical team won't listen. And Helen and Susan are running out of time to prove this isn't food poisoning—it's murder. Someone is using poison to bury a forty-year-old secret. And unless Helen and Susan can find out who the killer is and how they are delivering the toxin, more people will die before the ship reaches port. The past has caught up with the present. And the final trick is making witnesses disappear.

Helen hates cruise ships. But she wanted to see the Norwegian fjords, and a cruise was the way to do it. Ex-paramedic Susan would move onto a cruise ship permanently if she could. Retired Barrister Helen just wants a Jo Nesbø novel and to be left alone. Neither of them wanted Terry Davenport. He's the ship's guest speaker. An obnoxious ex-SAS soldier flogging his military memoir to anyone who'll listen. When his manager shows Helen and Susan a death threat naming four dangerous enemies from Terry's past, they assume it's a PR stunt. Then Terry plunges into the icy, 400-metre-deep Innvikfjorden in the dead of night. The Norwegian police call it a drunken accident. Helen and Susan aren't buying it. With the ship heading back to Southampton, Helen and Susan have hours to untangle decades of lies, grudges, and secrets before a killer disappears into the crowd at the Southampton cruise terminal. The fjords are beautiful. The buffet is excellent. And did someone just committed the perfect murder?