One of the lovely things about following comics in the late Silver and early Bronze Ages was the tendency of the publishers, especially Marvel, to make sure that loose ends were tied up. When a series fell victim to cancellation due to poor sales often the storyline would end abruptly, since the creators were working far in advance of the news that cancellation might come. So it wasn't unusual to see story lines find resolution in the pages of other comics some months after a character disappeared form the comic shelves. Avengers #72 is unusual in many respects, one is that it does indeed resolve dangling plot threads from the pages of the defunct Nick Fury Agent of SHIELD comic as well offer an update on Captain Marvel, who was at the time between issues of his off and on again run.
All that and the introduction of the crime cartel the Zodiac to boot. The Zodiac almost literally burst onto the scene in a relatively rare two-page spread by Sal Buscema and inker Sam Grainger. All of sudden the reader is presented with a dozen villains, eleven of them brand spanking new.
And later in the fifth issue of the run (Steranko's final issue of interior artwork) we learn more about Scorpio and see his potent Zodiac Key in play once again. It seems that Scorpio is someone from Fury's past, but we are not shown who that someone is. Seemingly Scorpio dies at the end of that story but when has that really ever worked.
So the stage is prepared for Avengers #72. Rick Jones, recently bonded by dint of the Nega-Bands to Captain Marvel of the Kree seeks help from his old allies the Avengers. He finds Captain America, who he thought had rejected him (it was in fact the Red Skull in Cap's body) and goes to meet the other Avengers. They quickly gather and learn that Nick Fury is dead, killed by an assassin named Bullseye (not that one).
Rick tells them how he had previously gone to Nick's apartment and encountered Scorpio and as quick as you can say Nega-Band Captain Marvel appears to battle the villain. He is brought low by the Zodiac Key and now Rick brings the Avengers a list of names. Those names are those of important city figures but before the team can act Scorpio appears on their communications screen and an explosion knocks them all out. When they awake they are captured by Scorpion in a hidden lair. Then the rest of the Zodiac reveal themselves to gloat, but thanks to Yellowjacket's control of bugs he is able to short-circuit the manacles and soon enough the Avengers and the Zodiac are fighting tooth and nail.
The battle takes a turn when Scorpio is revealed to be the seemingly dead Nick Fury himself and with that final twist the Zodiac escape. Fury reveals that the original Scorpio had been his brother Jake and that he had taken his place to infiltrate the cartel. Captain America offers Rick a place with the Avengers but now bonded to Captain Marvel he decides to head off on his own once again.
And that's how the Zodiac got started. We'll see their next nefarious scheme later.