"The Nutshell" is the fourth episode of the third series of the 1960s cult British spy-fi television series The Avengers, starring Patrick Macnee and Honor Blackman.

It was first broadcast by ABC on 19 October 1963.

The episode was directed by Raymond Menmuir.

[2] Steed and Cathy investigate espionage by a pretty burglar in "The Nutshell", codename for a top-secret underground nuclear shelter.

[3] They are not telling each other everything, and somewhere a traitor lurks.