The Challengers of the Unknown story has its penultimate chapter in Adventure 496 (Feb 83), by Bob Rozakis, Alex Toth and Frank Giacoia.
Investingating Professor Haley’s story, they discover that the dead uncle is really still alive. He had faked his death, but then dies anyway.
Red Ryan gets confronted by a casino owner he is in debt to. The man is accused of plotting the murder, but defends himself by pointing out that with Red dead, he would never get the money he is owed.
The story concludes next issue.