This episode is based upon the Ed McBain novel of the same name.
The set for the King house would be used again a few episodes later in Killer's Choice.
John Astin would soon be cast as Gomez Addams on The Addams Family.
Most of the territory covered by the 87th Precinct appears to be working class but apparently there are some wealthier sections as judged by the King residence.
Carella: How would you like to join the force, Mr. King?
King: It doesn't pay enough, Mr. Carella.
Cassidy: (over the phone) Enough with those Hopalong wisecracks.
The best episode of the series, hands down. It's no wonder famed Japanese director Kurosawa based one of his classic films from the novel on which this one was based. Perhaps he even watched the episode too.