DVX Grant was working with or associated with a scientist working on something called the PROMETHEUS DISC. Apparently, this was a miniature device that could revolutionize the energy industry and the DVX wanted this disc very bad!
That's why DVX Grant was there undercover: to steal the disc! At one point, the scientist is killed and the disc just disappears somehow and ends up in the hands of Luke Spencer, who realizes it's importance and hides it (one time taped to the top of a ceiling fan blade) at his night club.
Grant was also joined by two other DVX agents, a woman who works at General Hospital and a man who plays the piano professionally who have also been planted in Port Charles for the sole purpose of covering for and aiding Grant in the recovery of the disc.
Luke and Holly are eventually kidnapped by the DVX agents and hidden at an Indian Embassy for some reason i can't remember! anyhow, Luke and Holly of course realize that this Grant Putnam that they have known for a while is really a secret agent and appeal to him to help them escape: Grant does so by dropping clues about how he will help them and eventually replacing the bullets in a gun with make-shift blanks and tipping off Luke and Holly to drop and play dead when the piano player shoots them.
In early 1984, we learn that the REAL Grant Putnam was alive after being abducted for eight years (again, this EIGHT thing pops up!) and his identitiy and life stolen and assumed by the FAKE Grant Putnam, which we rechristened Grant Andrews. He set up DVX Grant for infidelity and attempted murder of Celia.
I guess Putnam had such a hard grudge over losing Celia and his life that he became the villan and the Andrews became a hero of sorts.
In 1988, a crazy REAL Grant Putnam retruned and abducted Anna Devane (Finola Hughes), but Scorpio and the gang made sure justice was served as Putnam was caught and Anna rescued. Grant kidnaps Anna and kept her hidden while Duke Lavery and Robert Scorpio compete as to who will find her first.