The Woman In Cabin 10 by Ruth Ware

This was meant to be the perfect trip. The Northern Lights. A luxury press launch on a boutique cruise ship. A chance for travel journalist Lo Blacklock to recover from a traumatic break-in that has left her on the verge of collapse. Except things don’t go as planned.

Publisher Description

Woken in the night by screams, Lo rushes to her window to see a body thrown overboard from the next door cabin. But the records show that no-one ever checked into that cabin, and no passengers are missing from the boat.

Exhausted and emotional, Lo has to face the fact that she may have made a mistake – either that, or she is now trapped on a boat with a murderer…