Edgar Diaz is the husband of Justine Diaz.
Eddie went undercover to take down some arms dealers code-named Argosy. The operation was ended and all the other agents came home, but Eddie didn't. Justine used information from Troy to track Eddie down and found him. When she confronted him, he said that he had stayed behind after the FBI had pulled the other agents out of the operation because they hadn't gotten the leader, Billy McLeland, and Eddie believed he could take him down if given more time. Justine set Eddie up at Ben and Rhys's place to stay the night. ("The Birthday Party")
Justine worked with Troy to learn the structure of Argosy. Then they used Rhys's contact to set up a meeting to get access to McLeland. Once they had the meeting set up between McLeland and Ben, they told Eddie and he revealed that he'd killed McLeland and taken over Argosy. He had them held hostage while he went to meet with Ben. Rhys was able to get the upper hand to free them and Justine happily arrested Eddie herself and told him they were getting divorced. ("The Knock-Off")
He's been married to Justine Diaz for over seven years. While he was undercover, he sent her an email saying that he'd fallen in love with someone else. He later told her it was so she would live her life, because he wasn't sure how long it would take to take down the arms dealer he had infiltrated. ("The Birthday Party")
When she learned he had killed McLeland and taken over Argosy, she arrested him and told him they were getting divorced. ("The Knock-Off")
He's an agent with the FBI. While undercover taking down an arms dealer, he ended up killing the leader and taking over. ("The Knock-Off")