Memory (or lack thereof) in Altered States.
What are you capable of when you are not completely conscious? The perils of sleepwalking create much tension in Bohjalian's The Sleepwalker, and its prequel, The Premonition. The latter is a super-short book in which Lianna Ahlberg introduces readers to her father and sister, Paige, and we learn about the mother's sleepwalking problem.
In The Sleepwalker, Laura's mother has vanished in the middle of the night. Laura teams up with the investigator (who happened to know her mother because of their connection as sleepwalkers), to discover what happened to her, This novel delves not only into the world somnambulism in general, but into the form of sleep disorder known as sexsomnia - which is someone who wants sex while in the sleepwalking trance.
This has a quietly developing tension as the details behind the disappearance are revealed after several twists and turns. The prequel isn't really necessary to follow the main story, but might add to it.
At first I thought that The Flight Attendant was a sequel to The Sleepwalker, but it turns out that it was not. Flight attendant Cassandra Bowden also has memory lapses in which she can't explain how things happened even though she was there. These blackouts, however, are not caused by Somnambulism, but alcohol-induced.
Binge-drinker Bowden wakes up in a Dubai hotel next to a dead person. Not just a dead person, but a murdered person. And, of course, she becomes the prime suspect. Bohjalian's storytelling draws out the investigation and Bowden's slow returning memories as she tries to continue with her life. At times, the details are a little slow-paced, but Bohjalian likes to surprise the reader with new suspects and plot elements that can keep you hooked until the very end.
Engaging and suspenseful stories for those sleepless nights.