Lucas Roberts left military school and came to Salem with his mother Kate. He soon befriended Sami Brady and the two began scheming. Sami wanted Austin, who was in love with her sister Carrie, and Lucas wanted Carrie, who was in love with Austin. Later, Lucas learned that his illegitimate father was Bill Horton and that Austin and Billie Reed were his maternal half-siblings.
When Lucas' friend Alan came to town, he raped Sami. She feared that nobody would ever love her, while Lucas was feeling rejected by Carrie. They were both seeking comfort, and they slept together. Soon after, Sami drugged Austin and tricked him into sleeping with her, too, by pretending to be Carrie.
After Lucas' mother Kate was apparently killed in a plane crash, he learned that Vivian had something to do with it and he blackmailed her into finding Sami and bringing her home in time to stop Austin and Carrie's wedding. Sami returned and revealed that she was pregnant with Austin's child. What Lucas didn't yet know was that he was her baby's daddy. That truth came out when Eric and Carrie got suspicious and started digging in the hospital records.
Lucas got Sami to help him with a new plot to convince Austin that Carrie was falling in love with Mike Horton. Lucas thought that once Austin gave up on Carrie, he could easily steal her from Mike.
Sami became engaged to Franco Kelly, but he was murdered, and she was charged with the crime. Lucas was the culprit, and he couldn't let Sami be executed. He confessed at the last possible moment.
Lucas didn't realize that his mother had paid Nicole five million dollars to marry him so that he would win custody of Will. The plan worked, but after Sami was released from prison, she worked with Nicole to get Will back. They were divorced less than a year after being married.
After being injured in a fire Kate set in the Kiriakis Mansion, Lucas was sent away to a rehab center. He came out of his coma and returned to Salem, but he was still partially paralyzed. He seemed to really want to make amends, but showed his true colors at Austin and Sami's wedding when he exposed the truth - that Sami had lied about him hitting Will - and ruined the wedding. Eventually, Lucas got joint custody of Will, whom he took with him for a summer to Africa.
Upon their return, Lucas went to work for Tony DiMera. He enjoyed his new power, but the stress drove him back to drinking. His AA sponsor, Maggie Horton, told him he would feel compelled to drink until he was truthful about his feelings. Lucas managed to control the drinking, even after Sami was injured at the DiMera Mansion and nearly died. While she was in the hospital recovering, Lucas kept fantasizing about her. He continued to help Sami adjust after she got out of the hospital.
Lucas was one of the main suspects when the Salem Stalker started a murder spree. When the Stalker's identity was revealed to be Marlena, Lucas comforted Sami. She and Lucas grew closer as he tried to help her through this difficult time, and they finally made love again. Lucas even proposed to Sami, but with a caveat: she had to promise to redeem herself and never lie to him again.
Sami and Lucas became engaged, but Kate did everything in her power to make sure they never walked down the aisle. She even brought Sami's ex, Brandon Walker, back to town. With Kate's help, Lucas "found" Sami and Brandon in bed together on the morning of the wedding, and he was devastated. As much as he loved Sami, he couldn't forgive her for this. He ripped up the marriage license and swore he never wanted anything else to do with her.
Lucas joined the team to rescue his half-brother Philip, unaware that Sami (disguised as Stan) had infiltrated the group with a plan of her own. Back in Salem, Lucas and Sami grew close again and became engaged. On their wedding day, Lucas' mother arrived at the chapel dressed in Sami's Stan costume. She exposed Sami's escapades, and Lucas dumped Sami at the altar. Austin, arriving for his half-brother's wedding, showed up just in time to comfort Sami.
Lucas accepted a job with Victor and traveled to California to investigate a possible takeover of High Style. To his surprise, his old flame Carrie Brady had left Mike Horton and was the head of the company. He convinced her to return to Salem. At first, Carrie and Austin seemed to reconnect, but she had feelings for Lucas, too.
Carrie agreed to marry Lucas, although she loved Austin, because she thought (through a plot of Sami's) that she could not have healthy children with Austin. She also believed that she was pregnant with Lucas's child. She and Lucas moved into an apartment across from Austin and Sami, who had seemingly reconciled. Shortly after Carrie's wedding to Lucas, she realized that she was never pregnant at all. That, along with the sexual tension between the two mismatched couples, resulted in a quick annulment for Carrie and Lucas. Austin and Sami became engaged, but she called off the wedding because she was being blackmailed.
Sami began a relationship with her neighbor EJ. Lucas became jealous and with Will's help, he and Sami were reunited. While away on a ski trip, snow caused the roof of a cabin to fall on Lucas. Sami left to find help and flagged down a car. The driver? EJ, presumably fleeing after shooting John Black. He told Sami that he would help her save Lucas if she let him have sex with her. She was disgusted, but unwillingly submitted in order to save Lucas' life.
Kate was desperate to find evidence that Sami was keeping a secret that involved EJ. She found a picture of Sami with EJ on the night of the blizzard and presented it at Sami and Lucas' wedding reception. To Sami's surprise, Lucas took her hand and told her he still wanted to be her husband. That night, Sami confessed all of her secrets to Lucas, including being blackmailed into having sex with EJ to save his life. They left for a honeymoon in New Orleans where they discovered letters from the past that revealed more about the Brady/DiMera feud. When they returned to Salem with the letters, Sami also discovered she was pregnant with twins. A DNA test showed EJ was the father.
When Sami gave birth, a second DNA test was done, and it revealed that Lucas was the father of the girl and EJ the father of the boy.
Sami asked Lucas for a divorce because Stefano had promised to end the Brady/DiMera blood feud if she married EJ. Lucas reluctantly agreed and Sami and EJ were married. Shortly after the ceremony, EJ was shot in the back and temporarily paralyzed. Sami couldn't fight her feelings for Lucas, and the two continued to see each other. When Sami refused to leave EJ because of Stefano's demands, Lucas sought full custody of their daughter, Alice Caroline Horton.
Eventually, a heartbroken Lucas admitted he was the one who shot EJ, and after a tearful goodbye to Sami, he was taken to state prison. When he got out, he walked in on EJ and Sami in bed. He couldn't believe Sami had betrayed him. She apologized and vowed to be true to him.
Lucas developed a friendship with Chloe. During a power outage, they made love in the elevator of the Salem Inn. Lucas proposed to Chloe, but she then started an affair with Dr. Daniel Jonas. Chloe called off the engagement, which upset Lucas deeply, and he turned to alcohol. He went to Daniel's apartment to confront him when a gas pipe blew and left him injured. He recovered, but with no memory of Chloe's affair with Daniel, and he and Chloe eloped.
Kate had learned about the affair and poisoned Chloe, framing Daniel. When Chloe recovered, she declared her love for Daniel. Lucas went to rehab, then moved to Hong Kong to start over.
Lucas returned to Salem per Sami's request. He announced his engagement to Autumn and reconnected with Will, who he was distressed to learn was working for EJ. When Lucas stayed in Salem, Autumn broke off their engagement. Thanks to Stefano taking control of Kate's businesses, Lucas lost his job, so he joined forces with Sami, the new CEO of Countess Wilhelmina Cosmetics, in both a business and personal connection.
Lucas and Sami were both shocked when Will came out. Lucas admitted that while he was surprised and worried at how the world will treat him, he assured Will that he would love him no matter what.
After EJ was framed for Stefano's murder, Sami went on the run with him to help him clear his name. Lucas declared their relationship over, for good.
