Adrian was infused with the same memories that Grant Gabriel had of childhood. He alleged to have been the first clone to survive Project Gemini, but said his body did not hold up well after his creation. He claimed that his body was aging on overdrive and he would be dead by Christmas, adding to his sense of urgency to expose Lex.
Adrian was willing to do whatever it took to shed light on Lex's cloning program. To that effect, he planted a bomb on Chloe Sullivan, and trapped her and Jimmy Olsen in a non-functioning elevator, and threatened to detonate it if Lois Lane didn't expose the truth about Lex's research on human cloning. Using Chloe as leverage, Adrian forced Lois to use her scheduled interview with Lex as a platform to get him to admit knowledge and responsibility of Project Gemini. Under his direction, Lois held Lex and Grant at gunpoint to try and force a confession.
However, Lex was able to overpower Lois and knock her unconscious. Adrian then stormed into Grant's office at the Daily Planet, and Grant realized that he, too, may be a clone. Lex then shot Adrian in front of Grant, telling Adrian that he wasn't his brother but a mistake. Just before Adrian died, he triggered the detonator on Chloe's bomb. However, Chloe and Jimmy were able to be rescued by Bizarro posing as Clark Kent.
As a result of Adrian's appearance, a rift emerged between Lex and Grant that was never resolved until Lex had Grant killed.
Below is the exact text of the first half of Lois's article about Adrian Cross (including Lois's original errors). 
Luthorcorp is the most prominent name in the Research and Development Industry. The Corporation is also a keen supporter of medical institutes such as Belle Reve. Lex Luthor, CEO of Luthorcorp, has taken a special interest in Meteor Inflicted patients, or those with special powers and has funded ground breaking experimental studies conducted at laboratories across the States. However, not everyone agrees Luthorcorp's intentions are honorable. Allegations about blatant disregard of Ethics Standard Practises by disgrunted and retired Luthorcorp Lab 33.1 employees imply Human Cloning practises at Luthorcorp Labs.
Enter Adrian Cross. Cross was born and grew up outside Philadelphia, PA. He graduated with Honor Roll status and played Point Guard at Homestead High. He obtained his Masters Degree in Journalism from Harvard University before landing his first job on the obituary beat at Liberty Times. He quickly progressed through the ranks and got noticed for the Editor gig in Alaska at the Anchorage Beat, first in Sports, then in Business. Cross established himself as a formidable and desirable Editorial force when suddenly this rising star was shot down. A reported "heart attack"...With his disappearance off the popular Circulation...
- Although Adrian's last name is never mentioned on the show, it is clearly visible in Lois's article about him.
- Adrian probably targeted Chloe and Lois simply because they are related. As cousins, they would be more easily manipulated than two strangers who worked together at the Planet.
- Adrian's aging appears to have been accelerated, similar to Grant's. Previous attempts at growth acceleration, such as Emily Dinsmore, resulted in severe chromosomal damage which left the clone without a moral center. Similar problems with Adrian's DNA would help explain why he has so few moral qualms about the blackmail and murder of innocent people who had nothing to do with Lex or Project Gemini.
- Even though Adrian and Gabriel supposedly had the same DNA, their eyes were different colors (Adrian's are blue, while Grant's are brown). This could potentially be explained by chromosomal degradation in Adrian's DNA.
- Adrian was an older version of Julian Luthor (Grant Gabriel), similar to an older clone of Lex Luthor in Season Ten's Lazarus.