Among the items in Charles Courtney's (Vincent Price) trophy cabinet is an alarm clock labeled "Cockrell 1905." This seems to be a nod to Francis M. Cockrell (and his wife Marian Cockrell) who wrote many scripts for Alfred Hitchcock Presents. In fact, Francis M. Cockrell wrote the first four episodes personally directed by Hitchcock. In addition, the clock is stopped at 4 o'clock, alluding to the premiere episode of the "spin-off" series Suspicion entitled "Four O'Clock" directed by Hitchcock and scripted by Cockrell.
This episode takes place in 1912 and 1914.
The title is based on the "perfect crime", one that is never detected or no evidence is ever found so that the perpetrator is never even sought.