A 20-hour, nonstop plane flight from London to Sydney provides the claustrophobic backdrop for this terrifying thriller from bestseller Mackintosh (Let Me Lie). Flight attendant Mina Holbrook trades shifts to join the crew of World Airways Flight 79, preferring to contend with sometimes demanding business class passengers than to face her rapidly deteriorating marriage to police detective Adam Holbrook. Mina is sure Adam has been sleeping with their Ukrainian au pair, who recently quit her job caring for their five-year-old daughter, Sophia. A few hours into the flight, Mina receives a note demanding she help an unknown terrorist group divert the plane. If Mina refuses, Sophia will die. What starts as a domestic drama focused on the Holbrooks' marital problems becomes the airborne equivalent of a classic country house mystery. The suspense builds as Mina, whose co-workers think she's shirking her duties, tries to determine who among the 353 passengers are part of the terrorist plot. Surprising twists propel the story to an unexpected finale. Mackintosh has raised her game with this one. Agent: Sheila Crowley, Curtis Brown (U.K.). (June)