The Doom Patrol (vol. 1) #90 (Sep. 1964):
“The Enemy within the Doom Patrol”
by Arnold Drake, Bruno Premiani

The Doom Patrol (vol. 1) #90

Title: “The Enemy within the Doom Patrol”

Medium: comic

Cover date: Sep. 1964

Publisher: DC
Written by: Arnold Drake
Art by: Bruno Premiani

7 characters in this story:

(Click links for info about character
and his/her religious practice, affiliation, etc.)
Pub. #
The Chief The Chief (Dr. Niles Caulder) hero scientist
  The Doom Patrol (founder) DC 176
Elasti-Girl Elasti-Girl (Rita Farr) hero
CBR Scale: U Protestant
The Doom Patrol DC 149
Negative Man Negative Man (Larry Trainor) hero
  The Doom Patrol
[test pilot disfigured in radioactive crash]
DC 154
Robotman Robotman (Cliff Steele) hero
  The Doom Patrol
[mind in robotic body]
DC 211
The Brain The Brain villain scientist
  Brotherhood of Evil (leader)
[disembodied brain]
DC 85
Monsieur Mallah Monsieur Mallah villain
CBR Scale: I uplifted animal
Brotherhood of Evil; gorilla DC 103
Madame Rouge Madame Rouge (Laura De Mille) villain
  Brotherhood of Evil DC 55

Reprints of this comic:
The Doom Patrol (vol. 1) #124 (June-July 1973): "The Enemy within the Doom Patrol"

We have seen The Doom Patrol (vol. 1) #90 (Sep. 1964) classified as containing a single story with three parts. The first chapter (part 1) is titled "The Enemy within the Doom Patrol." This is the title by which the overall story is known. The second chapter (part 2) is titled "The Deadly Replacements." The third chapter (part 3) is titled "One of You Must Die!"

On the other hand, we have seen this issue archived as an issue with two stories. The larger story is "The Enemy within the Doom Patrol," which is divided into two parts. There is a second story in the issue titled "The Deadly Replacements."

However one divides this issue - whether into one "story" or two stories or three stories, it is largely immaterial. This is because all three of these chapters or sections had the same creative team, all have the same characters (the four members of the Doom Patrol and the three core members of the Brotherhood of Evil) and all three sections chronicle events which take place in the same timeframe and tightly relate to each other. On balance, it seems simplest and most accurate to regard this entire issue as a single story.