Turnaround at Sea (1, #2)

Grace and Philip Partain plan a cruise to revive their 20-year-old marriage, after Grace's rescue from would-be kidnappers. She is pregnant at forty and wants to invite her new friend (young, pregnant Sadie McClarron), who helped her escape from drug dealers, to live with her and Phil. It all seems doable until Phil disappears, and Grace finds herself alone on the cruise ship. She is terrified and the suspense begins.