The theft of a famous painting leads to murder and many suspects on a plush train speeding from Paris to Rome.

After receiving an advance inheritance, a bored London couple set off on a world cruise hoping to rejuvenate their marriage and escape their dull routine. But newfound wealth and freedom only expose deeper cracks in their relationship, as each becomes infatuated with someone else. Their journey through exotic ports and mounting disillusionment ultimately brings them face to face with the fragility—and resilience—of love.