Jack Sparling joins Arnold Drake for the final issue of the Plastic Man series, number 10 (May/June 1968).
The villain in this story has created an army of miniature soldiers, which he sends out against Plastic Man. They don't do a lot of damage to the resilient hero, but do wind up sending Gordy Trueblood to the hospital.
Plas winds up giving Gordy a blood transfusion, which of course results in Gordy gaining the same powers that Plastic Man has. Gordy decides to become a hero as well, and adopts a costume very similar to that of Plastic Man. He tries to fight crime in a more serious manner, but has little success, and Plas has to keep getting him out of trouble.
Meanwhile, the villain, Marcel Mannequin, arranges to have his dolls at a party thrown by Mike DeLute's mother. While Plas is busy dealing with Gordy and other crimes, he will have his dolls rob the partygoers.
Sparling really doesn't do a very good job with the art. Despite the cover, there are virtually no scenes in which Gordy and Plas are using their powers simultaneously, when it would be such an obvious visual treat.
Plas and Gordy make it back to the party, and defeat Marcel Mannequin and his doll army. Gordy still has his powers as the story ends, and likely would have maintained them had the series run any longer. So I think we can all be glad that it got cancelled at this point.
The Plastic Man book would get revived in 1976, and continue the numbering, though the supporting cast would all be dropped, as would the notion of this being Plastic Man's son. The next time Plastic Man is seen is a couple of years down the road, teamed with Batman in Brave and the Bold.