This exceedingly rare mystery, first published in 1956, makes its triumphant return to print for the first time since its original appearance.

On a bright autumn morning, Superintendent Macdonald boards the plane bound for Vienna to visit his old friend Dr. Natzler. His detective's eye notes some unusual passengers including Elizabeth Le Vendre, new secretary to the diplomat Sir Walter Vanbrugh—but this is supposed to be a holiday. After arriving with the Natzlers and crossing paths with Elizabeth again, Macdonald settles into the trip as best he can, determined to relax for once.

But when Elizabeth is reported missing and a string of violence and murder encircles Vanbrugh and Natzler's social set, Macdonald's short-lived stint as a tourist comes to an end—and the race to stop a killer on the loose begins.