After the fight between Tina Greer and Jeff Palmer at Belle Reve Sanitarium, Jeff disappeared. Some say that Jeff died that day. Others say that Jeff works in secret, aiding the Justice League. Some others say that Jeff Palmer was driven to the brink of madness that day by Tina, and spends his nights plotting his ultimate revenge against the Legion of Doom.
A couple of years after Jeff's disappearance a new metahuman group emerged, known by several names including 'Earth First' and 'The Avant Guard'. They were a xenophobic group that opposed the interference of alien beings in what they considered to be "Earth matters", and were lead by a mysterious and powerful being known as the Emerald Empress. 'Earth First' quickly drew former members of several groups including the Hand of Vengeance, and became very powerful.
One of their members known as 'The Phantom' was said to have the power to make himself invisible, an ability that was once shared by Jeff Palmer. He was also said to be a fierce critic of Tina Greer and the Legion of Doom.
A few weeks after the Justice League learned of 'The Phantom' a Justice League compound was attacked by Earth First. The league officers who were guarding the facility were overwhelmed and were forced to retreat. Two officers, 'Steel' and 'Ice', were killed in the attack.
The facility had been used to house metahuman prisoners who the league considered to be too dangerous for Stryker's
After the attack, the Justice League determined that some of Dr. Jeff Palmer's equipment had been stolen. Their suspicions about Jeff were confirmed. He was the 'The Phantom', as they had suspected.
Greg was devastated. He set out to find Jeff himself. He discovered that Jeff emitted a rare form of radiation when he was invisible, and began searching for him.
(Photos from left to right: Chad E. Donella as Greg Arkin/'Captain Atom', and from the DS9 episode 'Siege of AR-558' Patrick Kilpatrick as 'Steel', Bill Mumy as 'Blue Beetle', Annette Helde as 'Ice', and Raymond Cruz as 'Red Tornado')