Prisoner 21 has all the usual elements of prison stories.
Donne Avenell was the writer of this story and art is by Heiner Bade.
Avenell ‘borrowed’ two ideas - the first from the famous movie Bird Man of Alcatraz.
The second from the history of Alcatraz. Alcatraz is the notorious former federal prison, built on a rocky island in San Francisco Bay (USA). It was escape proof and nick-named ‘The Rock’. Many attempts were made to escape but only with disastrous endings!
Prisoner 21 - a clever plot! And with one of the more unusual identities The Phantom used.
And the stark simplicity of Bade’s art makes it work— old fashioned and almost quaint.