Dario arrived in Salem as a petty thief. He stole Gabriella's earring and Melanie's necklace. After several trips to the pawn shop and some mysterious meetings with a man on the docks, it was revealed that Dario came to Salem to investigate Arianna's murder -- a case that had gone cold in the Salem PD.
Dario and Melanie immediately butted heads, as Dario was quick to accuse all of Arianna's Salem friends of not carrying about solving her case. Melanie used some of her divorce settlement from Philip to put out an award for information on the murder. While working together to solve Arianna's murder, Dairo and Melanie began to have feelings for each other.
Dario was the first person that Melanie called when she interrupted Brady's assault on E.J. and needed help cleaning up the crime. Reluctantly, Dario agreed to help Melanie. Eventually, Daniel, Jennifer, Carly, Maggie, Victor, Nicole, Taylor, Bo, and Hope all kept the crime a secret to protect Melanie's involvement as well as Brady.
Brady offered Dario a job at Titan, claiming that the two of them had gotten off on the wrong foot. The real reason was that Brady did not want Dario around Melanie. So, Brady assigned Dario to the hardest manager, who demanded overtime from all his employees.
But Dario proved to be up to the challenge. He quickly impressed his manager and was rewarded with a promotion. The only downside was that the job was in Argentina. Knowing that she couldn't stand between Dario and this career opportunity, Melanie said goodbye to Dario and he moved to Argentina.