After a life of crime as a Peruvian drug lord and stealing other dealers money and drugs, Marco Annicelli, somehow ended up in a Peruvian prison. He spoke of Marisa, the woman he loved who was hooked on drugs, whom he helped overcome the addiction, but he had to leave her behind to protect her when his enemies were on his trail.

The rich, ruthless, and powerful, American business mogul Victor Newman discovered that Marco bore a strong resemblance to Victor's nemesis, Jack Abbott. Victor went to Peru and paid someone off to secure Marco's release and Marco spent months learning how to speak without his Spanish accent and pass himself off as Jack to Jack's family, friends, and the love of his life Phyllis by watching videos of Jack.

Meanwhile Jack Abbott and Phyllis went to St. Barts to get married. Although a sudden storm interrupted their wedding on the beach, they were married in their hotel room. But afterward, Jack was kidnapped courtesy of Victor, and Marco took his place impersonating Jack. Marco later admitted that he had taken Jack's place for a short time months before after Jack had emerged from a building collapse just to see what it felt like to be him.

Marco returned as Jack from his honeymoon to Victor's accusation of his hacking the Newman computer system. Marco smugly suggested Victor talk to his lawyer. Later Jack's brother and sister, Billy and Ashley tried get "Jack" to step down as Jabot Cosmetics CEO. Instead Marco fired Billy, and told them the war was over, a truce had been called, and he had made a deal with Victor to merge their companies into Newman-Abbott Enterprises.

Victor warned Marco to stop being so cocky and taking advantage of his new-found power, that his out of character over-zealousness with Jack's new wife Phyllis, spicing up his wardrobe, and buying a $400,000 red Ferrari was bound to expose the ruse. Meanwhile back in a hut on St. Barts, Jack was being held hostage. Jack managed to get hold of a cell phone and called his son Kyle, but instead Marco answered. Kyle was driving the new Ferrari, and crashed it into a tree. Marco ended up in a coma. With a loving Phyllis sitting at his bedside, Marco woke up and remembered "Red" and how much he loved her. Once they were home again, Phyllis began witnessing "Jack" having nightmares in which he spoke Spanish.

Marco threw a party as Jack at the Genoa City Athletic Club to celebrate the merger. He convinced Ashley and Billy to pull together to make it a success, to bury the hatchet, and be an example. "Jack" announced that he was funding a new pediatric wing at Genoa City Memorial, dedicated to the memory of Cassie Newman. Tobias Gray, the lab assistant who had spied on Jabot for Victor, crashed the party and sat on the bar regaling everyone about their family secrets. Billy ushered him out, and Tobias crashed his car while driving away. Marco showed up at the hospital in time to see Tobias die, and looked relieved. Victor accused Marco of pinning the murders on Tobias and getting rid of him, telling Marco to watch his back.

Marco realized in talking with Gabriel Bingham that Gabriel and Jack had a scheme going, and Gabriel was actually Victor's thought to be dead son Adam after plastic surgery. Marco wasted no time in going to Victor to tell him who Gabriel really was, but intending to put one over on Victor, Marco told Victor that Jack was Gabriel's father instead. It was revealed in conversation with Victor that Austin Travers had been murdered by Marco. After Austin had video taped Marco and Jack in the park at the same time, Marco paid police detective Harding to erase the footage from Austin's hard drive. But Austin woke up and caught Harding, so Harding murdered Austin. Courtney had made the same discovery watching the security tape from the park, had shown it to Harding, and Harding murdered her to protect Marco.

Meanwhile, Marco discovered that Jack (captured and thought to be Marco) was being ransomed dead or alive to the highest bidder, most of whom wanted Marco dead. Marco won the bid on Jack for ten million dollars. Marco got Kyle to wire money to an account, supposedly to buy a shipping company, to pay the ransom. But then Marco got word that the ship Jack was being held on had blown up with no survivors. Phyllis walked in on Marco as he received word that his former lover, Marissa Sierras, had been with Jack and had died as well, and accused him of plotting against Victor again. Marco told Phyllis a woman named Manuela whom he once loved had died with her new husband in a ship explosion. Marco told her he would not let Victor own and control him. Asking wouldn't she be happy if they could get control of both Jabot and Newman, everything they had ever dreamed of, but Phyllis pushed him away, asking, "Who are you?"

Marco called a meeting with Chelsea, Gabriel, Billy, Kyle, and a hospitalized Ashley to be filled in later, convincing them it was time to overthrow the king and take Newman-Abbot for themselves. He explained how the money he had Kyle draw to buy a shipping company actually was transferred into a dummy account in Victor's name, and how they were going to be diverting funds to the account, intending to take Victor down for grand larceny and corporate fraud. Billy was tasked with keeping Victoria from finding out, and Marco insisted that Billy and Gabriel bury the hatchet. When Marco told Ashley the plan, she refused to be involved, calling it illegal embezzlement, but Billy talked her into it.

Later Marco shocked Victor by telling him that he had paid ten million dollars to have Jack killed. Victor went for his gun in his desk drawer, but Marco had it, and aimed it at Victor. Victor scowled, "You don’t have the guts." Marco reminded Victor that he was not Jack Abbott. Victor called Marco just a thug in a $2000 suit and pointed out that the gun was empty. Marco pulled the trigger several times at Victor's face, they both laughed, then threatened each other with exposure. Marco told Phyllis, and Victor told Neil, that the other might kill them. Phyllis confronted "Jack" after finding out about his secret long lost son Gabriel. Marco talked his way out of her wrath in that he had just found out himself, they hugged, and Phyllis felt a gun in Marco's pocket.

Gabriel became suspicious and asked Marco some trick questions. When Marco failed the test, Gabriel asked him who the hell he was. Gabriel said he knew what it was like trying to impersonate someone. Marco admitted that he had begun testing his impersonation of Jack all the way back to having sex with Kelly in the supply room. Marco pulled his gun when Gabriel threatened to go to the police, and confessed that Jack was dead, calling it an unfortunate accident. Threatening to expose Gabriel, Marco told him that he was going to help Marco fake Jack's death and blame Victor for it. He promised Gabriel that joining him would not only get him revenge against Victor, but as the eldest heir to Jack, he would get Jabot, plus the love of Chelsea. Realizing he had everything to gain, and nothing to lose, Gabriel agreed to help. Marco's plan was to goad Victor into shooting him, while wearing a bullet proof vest. Marco called Nikki to meet him in the park, Victor refused to let her go, and went instead. Victor shot him, and Gabriel came out of hiding. Gabriel promised to cover it up in exchange for Newman-Abbott, and Victor agreed. Then Marco arrived, and both of them were shocked to realize it was Jack on the ground covered in blood, but still alive. Marco left just before the police arrived.

Marisa let Marco into her hotel room, thinking he was Jack. They fought, he kissed her, she bit him, and said that she hated him. Marco booked a jet to take them to the Caribbean, but Marisa pulled a gun on him, telling him that she was turning him for what he had done to Jack. Marco dared her to shoot him, but because she still loved him, she could not. He sweet-talked her into flying away with him, but on the way, Marisa realized he was taking her somewhere else to kill her. She grabbed the steering wheel, the car veered off the road and into a lake. Marco did not surface and was assumed drowned by Marisa, who staggered into The Underground bar wet and shaken.

When the car was found, there was no body inside. Marco showed up at Abbott Manor and attempted to fool Phyllis that he was Jack, but she realized he was not. After Marco made another attempt at being a Casanova, she hit him over the head with a vase and knocked him out. She called Jack to let him know, but while her back was turned, Marco escaped.

Marco hid out in the Abbot cabin with the aid of his partner in crime, Detective Mark Harding. As they talked it became clear that after Austin had videotaped Marco and Jack in the park at the same time, Marco had paid Harding to erase the footage from Austin's hard drive. But Austin woke up and caught Harding, so Harding murdered Austin. Courtney had made the same discovery watching the security tape from the park, she had shown it to Harding, and Harding murdered her too. Harding became remorseful, returned all the payoff money to Marco, and left. A confrontation with Noah also revealed that Harding had killed Tobias Gray.

Jack enlisted Marisa's help in luring Marco to the Abbott cabin, and Marco ended up tied to the bed. Jack and Marco exchanged heated threats, as did Phyllis with Marco, but neither could kill him like they wanted to. Marco seethed at them, calling them cowards. Jack was ready to go to the police to get justice against Victor and Marco, but Phyllis talked him out of it. Victor arrived, and talked them into letting him return Marco to prison in Peru, as they all had too much to lose if the truth ever got out. On the way there, Victor had one of his men cut off Marco's ear so he could never be mistaken for Jack again.

A month or so later, a young handsome man named Luca Santori showed up at The Underground looking for his wife, Marisa. He told her that Marco was in prison, and had told him where to find her as payback for her part in putting him there. Luca was told by Victor that Marco had been killed by another inmate in prison.