‘Then the rhythm of the train changed, and she seemed to be sliding backwards down a long slope. Click-click-click- click. The wheels rattled over the rails, with a sound of castanets.’
Travelling home from a European holiday, Iris Carr ends up alone at the station after a quarrel with her friends. Struck by a mysterious assailant and waking up just in time to board the train which will take her on her journey to London, things seem to be looking up after a chance meeting with the affable Miss Froy.
But when Iris passes out and reawakens, Miss Froy is nowhere to be found. The other passengers deny any knowledge of her existence and as the train speeds across Europe, Iris spirals deeper and deeper into a strange conspiracy.