Iris Carr is shocked: Miss Froy, her neighbor in the train compartment, has disappeared without a trace. Moreover, the rest of the fellow travelers not only did not notice this, but also claim that there was no Miss Froy at all! Perhaps Iris was a victim of sunstroke? Or did she just dream the disappearance story? Or maybe there is a reason why other passengers chose to “not notice” the crime?.. In a provincial town there are rumors about a mysterious maniac killing lonely girls. However, Helen Capel, who recently got a job as an assistant to the pedantic Professor Warren, is sure that she has nothing to fear - the house is reliably guarded by servants. But it soon turns out that the killer is one of the inhabitants of the mansion, and Helen herself is next on the list of his victims...