Antonio had been in Statesville Prison for six years for a murder in a pool hall and his mother, Carlotta, had severed all ties with him. In 1995, Police Commissioner Bo Buchanan made a deal with Antonio to release him early if he helped Bo flush out the dirty cop who was selling stolen guns to the teenage gangs in Angel Square. Antonio worked with police officer Andy Harrison and eventually they learned that her partner, Det. Nick Manzo, was the cop stealing and selling the guns. All hell broke loose when Manzo realized Andy and Antonio were working for Bo, and he set up Andy to look like the dirty cop. Antonio was stabbed while attempting to create a peace treaty between the two rival gangs, and Andy shot a gang member who was about to kill Antonio's brother, Cristian. Antonio ended up in the hospital with a stab wound, but was alive. But Manzo made it look like the teen Andy shot was unarmed and made Andy and Antonio look as if they were selling the guns.
Andy went on trial for murder and for being the accused gun runner, with Antonio being set up as her lover-accomplice. Throughout her trial, evidence piled up, and Antonio and Dylan tried to convince Linda, a local girl who liked Antonio, to come forward with the truth- that Ice Dixon had a gun and Andy shot him to save another's life. Antonio talked and flirted with Linda, trying to get Linda to testify for Andy. Andy was convicted, but a day later the verdict was overturned when Bo and Linda tricked Manzo into confessing and Andy and Antonio were released. The next few months were devoted to Antonio and Andy slowly building up a relationship. Seven months after they met they made love on Valentine's Day and from that day forth, Antonio and Andy were fully committed to one another.
Antonio took a loan from loan shark R.J. Gannon to buy the Angel Square diner for his mother and started working for gangster Carlo Hesser to repay the loan and to send his brother Cristian to college. He didn't tell Andy about it because he didn't want her to be compromised in her job. When Andy found out he was working for Carlo, she tried to be a cop and a criminal's girlfriend, but was suspended by Bo for protecting Antonio, which was actually a loyalty test the commissioner had set up for her. Andy and Antonio broke up for a few months, then Antonio went secretly undercover with Bo to trap Carlo. Antonio and Andy reunited when she found out he was working with the police, and she was reinstated to the force by a forgiving Bo.
Things were looking up, until Antonio was charged with Carlo's murder. Andy never wavered in her belief in her lover's innocence, even when she found incriminating evidence and turned it in to Bo. His trial was full of ups and downs, and Andy even was forced to testify "against" her lover, but Antonio was eventually cleared of all charges when Mortimer Bern testified that he saw Alex Olanov shoot Carlo. After the trial, Andy and Antonio went to NYC and re-affirmed their love for one another. Antonio's name was cleared for the original pool hall murder and Andy found an organization for Antonio which would pay all his law school expenses if accepted. He was, and with this great news, he proposed to Andy-who accepted.
The next few weeks were filled with Andy working to connect R.J. Gannon with some Atlantic City mobsters. An old nemesis, Javier, ruined Andy's undercover operation and attempted to kill her, Antonio got there in time to save her and for his troubles his grant was taken back. Andy, Nora Buchanan and Hank Gannon fought for Antonio and his grant was restored. He was also accepted to Berkeley Law School and it was decided they would move to California. Antonio and Andy were married, had a reception in Angel Square and left for their new life in California. Antonio returned briefly in 1998, to help his brother-in-law Max Holden when his children were kidnapped.
In 2000, Antonio returned to Llanview to help his brother, Cristian, who married Roseanne Delgado and then learned she had been lying to him. It turned out that Andy had had an affair with her police partner, which was why Antonio had left her. Andy and Antonio eventually got a divorce and Antonio started a relationship with Roseanne, who was now divorced from Cristian. Sophia, Antonio's partner, was also in love with him and when she called him for help, Roseanne didn't pass along her message. When Antonio found out that Sophia could have died because of Roseanne's actions, he broke up with her.
He became furious when he discovered R.J. had hired a hit man to go after his brother, since he and Cristian were working together to bring him down. R.J. refused to say anything to put Keith away for good, and that made Antonio very angry. He was taking college classes at Llanview University where he met Professor Keri Reynolds. She made life difficult when she turned down a paper that could get him a promotion. Finally, he fixed it to her satisfaction and the two had feelings for each other. Antonio was shocked to discover that Keri was R.J.'s daughter, which Keri herself did not know until recently. They had problems due to that, especially since R.J. kept getting in the way.
Carlotta was not pleased either with Antonio dating R.J. Gannon's daughter, and was not quiet about it. Finally, Keri and Antonio decided no matter what their families thought, they were going to stay together. Antonio tried hard to get Carlotta to accept Keri, but soon after the birth of his daughter, Jamie, his relationship with Keri fizzled out. Deeply jealous over the end of her and Antonio's relationship, Keri filed for sole custody of Jamie and tried to make Antonio out to be a bad influence on the child. Although Antonio was able to fight Keri and obtain joint custody, the victory was bittersweet when Keri wound up dead! Though accused of Keri's murder, Antonio's new girlfriend, Jessica Buchanan, was able to find new evidence that cleared him and prove that Keri had committed suicide. Jessica was also there for Antonio when his brother, Cristian, was believed to have died.
After learning that his mother, Carlotta, was the sister of infamous crime lord Manuel Santi, Antonio immersed himself deep undercover to investigate the crime family and gave Jamie to R.J. to look after, infiltrating himself in the life of local bar owner Sonia Toledo, who turned out to be connected to the Santis. Sonia eventually led him to Tico, who Antonio began to suspect was El Tiburón, the head of the Santi crime family. At the same time, he also met Santi governess, Angelina Paredes, and felt a strong connection to her. Through the course of his investigation, Antonio learned that his entire life was based on a lie; he was really Manuelito Santi, the eldest child of Manuel and Isabella, who had been adopted by Carlotta and Diego as a child to protect him from Manuel.
The news of his true parentage nearly destroyed Antonio. Unable to cope with what he had learned, he broke off his relationship with Jessica, and fell into bed with Sonia, whom he had learned was an INL agent. The two continued to investigate El Tiburón, and at one point, they even believed that Isabella had been the mastermind. Antonio and Sonia were eventually able to prove that Tico was El Tiburón, but then Tico ended up dying in the hospital. While the whole town wondered who killed Tico, Antonio was shocked when his brother Cristian turned up alive and well. The joy was short-lived, though, as Antonio was soon devastated to learn that Cristian was an imposter brainwashed to kill him on Tico's orders (in reality, it truly was Cristian, but he pretended he was an imposter).
After grieving for his brother again, Antonio became more determined than ever to get his life back on track. Regretting his decision to cast Jessica out of his life, Antonio had begun campaigning to get her back while 'Cristian' was still around, even when she suspected him of being her stalker. When R.J. arranged to have two marshals pick Jamie up at Antonio's place (thanks to a writ of temporary custody) on the first real visit Antonio had with his daughter since giving her to R.J. months earlier, Antonio was devastated. Jessica vowed to stand beside him while he fought R.J. for custody, but when Jamie and Jessica nearly died in a fire, Antonio began wondering if staying close to Jessica was best for Jamie. Antonio eventually won custody of Jamie after John burst into the courtroom and arrested R.J., and was overjoyed when Jessica was back and pregnant, only to learn that Jessica had an alter named Tess and had also been intimate with another man. Antonio was convinced the baby was his, and was determined to get Nash Brennan out of their lives.
Antonio was thrilled when the baby was born and, shortly after, Jessica managed to regain control after months of Tess being in control. But he was devastated to learn that Nash was the father of the baby, named Bree. Nevertheless, Antonio was determined to forge ahead and have a future with Jessica and Bree, whom he planned to raise as his own daughter. Jessica and Antonio become engaged and marry in November 2006. Soon after, however, Jessica and Nash began to develop feelings for each other. Jessica resisted her feelings and even agreed to adopt Antonio's daughter, Jamie. On the day of the adoption hearing, as Nash was preparing to leave town, Jessica left the hearing and she and Nash meet at the stone quarry, where they gave into temptation and made love. In May 2007, Jessica was about to tell Antonio that she wanted to be with Nash when she collapsed. She had contracted Hepatitis C as a result of Tess' wild lifestyle and needed a liver transplant. While waiting for a suitable donor, Jessica admitted her feelings for Nash to Antonio, who was furious and left town with Jaime. After learning that Antonio was a donor match, Nash tracked him down and convinced him to return to save Jessica. Antonio donated his liver, but Jessica rejected the transplant and had to have another transplant from another donor. Jessica and Antonio divorced in July 2007, paving the way for her and Nash to marry.
Meanwhile, Antonio got closer to his colleague, police officer Talia Sahid. Talia had a crush on Antonio but kept it secret, believing that Antonio was reeling from the end of his marriage and that any romantic tension would ruin their friendship as well as their professional relationship. Talia spent the Thanksgiving 2007 holiday with Antonio and his family and shared a sensual dance with him in his mother's diner. Talia then impulsively kissed Antonio and confessed her feelings for him. Antonio, still hurt after his divorce, rebuffed her advances politely. Their personal and professional relationship quickly began to disintegrate, and after a few awkward exchanges at work, Talia requested a transfer to the quiet neighboring township of Cherryvale. Antonio and Talia argued over her transfer, but Police Commissioner Bo Buchanan reluctantly agreed to her request.
Antonio soon realized that he was only waffling about his feelings for Talia out of fear of being hurt again, and decided he could not pass up this opportunity for true love. On New Year's Eve, he raced to meet her at the bus station, taking her in her arms and passionately kissing her. Talia agreed to give Antonio a second chance at pursuing a tentative romantic relationship, and happily decided to stay in Llanview. Unfortunately, when the two officers returned to work, Bo informed Talia that despite her change of heart, the work transfer was final and she was expected to report to Cherryvale immediately. Talia and Antonio resolved to continue their long-distance relationship as best they could on their "off-hours," but their work schedules proved more and more incompatible. Talia eventually managed to switch places with Antonio's new partner and transferred back to Llanview, resuming her romance with Antonio.
Their relationship quickly seemed put to the test, however, after Bo Buchanan was ousted and replaced as police commissioner by renegade former FBI agent Lee Ramsey. Antonio seemed to remain loyal to Ramsey, while Talia and Detective John McBain did not trust him. After it appeared that Talia and John had slept together, Antonio and Talia publicly broke up within ear shot of Ramsey and other officers. Antonio more than ever was brought under Ramsey's wing. However, it turned out that the breakup had been a ruse concocted by Talia, Antonio and John to entrap Ramsey. Commissioner Ramsey enlisted Antonio in his plot to steal the Crown Jewels of Mendorra, while they were in police custody, but he was murdered in June 2008 before he could be brought to justice. Tina Lord, who had been masquerading as the Mendorra princess, ended up with the jewels, but soon found her life in danger when Jonas Chamberlain, the U.S. ambassador to Mendorra, came looking for them.
Talia then inexplicably aided Jonas Chamberlain in kidnapping her roommate Sarah Roberts, who was Tina's daughter. Soon Antonio and Cristian discovered that Jonas had both women; they and Tina accompanied Jonas back to Mendorra in order to make an exchange: Sarah and Talia for the Crown Jewels. Talia and Sarah were being held in a jail cell beneath the royal palace when in walked Carlo Hesser, who it turned out was the real mastermind behind the kidnappings. He had disappeared from Statesville prison with the help of corrupt Lee Ramsey.
Talia as it turned out was Carlo's youngest child. Carlo intended to force Talia to marry Jonas, the true heir to the throne and Carlo's puppet. Talia protested and stalled, but went through with the royal wedding on July 31, 2008, to save Antonio and her friends from harm. Talia stayed behind as her friends returned to Llanview, but soon Antonio, Cristian and Sarah returned and freed Talia. Talia apologized to Antonio for having kept her true parentage a secret, and Antonio forgave her. Back in Llanview, Talia rejoined the police force and she and Antonio continued to grow closer.
Cristian, however, failed to return to Llanview on a connecting flight and Antonio and Talia soon realized that Carlo had escaped from Mendorra and was behind Cris' disappearance. Cristian, who had been locked in a Columbia prison, managed to get out with the help of Vanessa Montez, the wife of the prisoner Cristian had replaced. In exchange, Cristian promised to help Vanessa and her step-daughter, Lola, gain safe passage from Columbia to Llanview, where they would be safe from Vanessa's husband, Ray Montez. Just before departing, Cristian managed to call Sarah and tell her that he was alive. Antonio and Talia traced the call to Columbia, and they and Sarah booked a flight to Columbia so they could locate Cristian. Cristian, meanwhile, was on his way to Llanview with Vanessa and Lola. They arrived at the airport and were greeted by a stunned Sarah, Antonio and Talia.
Meanwhile, Antonio was promoted to lead detective at the police station after John McBain resigned while investigating the mysterious woman being held in Todd Manning's home, who turned out to be Marty Saybrooke. Antonio was called to Todd's home after John discovered Marty and subsequently beat up Todd, and Todd was taken to the hospital and later arrested. Antonio was disgusted when he learned that family friend Tea Delgado had returned to town to represent Todd during his trial. When Lee Halpern, one of the key witnesses who was going to testify against Todd, was found stabbed to death in Todd's home, Tea falsely claimed that she killed Lee in self-defense. But Antonio didn't believe the story and was convinced that she was covering for Todd. Antonio broke up a fight between Todd and Wes Granger, a newcomer in town who had befriended Marty, during the Go Red Ball, and Wes subsequently was found stabbed to death in his hotel room. Antonio, meanwhile, left town for a few weeks and Talia explained that he was on assignment. When he returned in March 2009 he told Talia that he was working to track down her father Carlo Hesser. Talia pleaded with him to let it go, but Antonio said he needed to bring Carlo to justice to end that chapter in their lives. He told Talia he was leaving again but would return shortly. He left daughter Jaime in his mother Carlotta's capable hands and left for parts unknown.
The following month, Talia was stabbed to death by a serial killer after going to Dorian Lord's home searching for John McBain, who had been set up to look like the killer. Hearing the news, a devastated Antonio returned to pay his last respects to Talia, whose body was in the city morgue. Antonio visited John, who was being held in jail, and pleaded with John to find the real killer before helping him escape. Antonio returned to Talia and said a final goodbye before taking his daughter and leaving town for good.