Diamond smuggling (sometime prior to 2014-2015)
Serena Mason came to Salem in the winter of 2014 to do medical research from a story that she was working on. But, she selected Salem University Hospital so that she could come back to see if she could rekindle things with ex-boyfriend, Eric Brady.
Eric and Serena met in Africa, while she was there on a story assignment. They fell in love. But, when Eric felt drawn to the priesthood, Serena did not stand in his way. However, as soon as she heard that Eric had left the priesthood, she wanted to see if there was another chance for them. Eric was happy to see her when she arrived in Salem.
Eric wasn't the only friendly face in Salem. His entire family recalled meeting her one time in New York and were thrilled that she was back in Eric's life. Also, while living in Europe, Serena met and became friends with Melanie Jonas. Melanie moved back to Salem at the same time as Serena.
While her friendship with Mel and her feelings for Eric were real, Serena was actually in town on other business. She was sent to swap out an elephant statue Eric had from Africa with a fake. Eric's statue contained a secret compartment, which was filled with blood diamonds that Serena was smuggling out of Africa.
Her plans to snatch the statue were often foiled by Nicole -- with whom Serena butted heads many times, especially over Eric. Serena's troubles got worse when her boss, Xander Cook, arrived in Salem to see what was taking her so long aquiring the diamonds. Serena was not happy to see Xander. But, within a few weeks, she was able to give the diamonds to Xander, and she received her payment. Happy to be free of Xander, she focused her attention on Eric.
But Xander wasn't done with her. He'd known Eric in Africa as well and wanted to rekindle the friendship. But, Serena was adamant that Eric stay away. She stalled on providing the reason why for months. Finally, Eric got her to explain. After Eric left Serena to join the priesthood, Serena turned to Xander. She was drawn to his dark and exciting side. He talked her into smuggling diamonds with him. She hid some in her elephant statue. However, when Eric was packing to leave Africa, their statues got accidentally switched, and Eric returned to the U.S. with Serena's diamonds. So, she had to come after them.
Eric was furious with Serena for lying to him. He felt as though their whole relationship had been an excuse for her to get close enough to him to swap the statues. So, he ended their relationship.
Nicole wouldn't let up. Eventually, she looked into Xander and discovered that he was involved in some criminal activity. Serena warned Nicole to stay away from Xander, but didn't give Nicole any specifics. Assuming that Serena was just lying again, Nicole kept digging. But Xander really was dangerous. He tracking Nicole down at work one night and attacked her. Eric came to her rescue and Xander took them both hostage. They fled from him.
Worried that she couldn't get a hold of Eric, Serena went to look for him. She enlisted Daniel and Brady's help as well to look for Nicole. Eventually, they found Nicole and Eric trapped in a heating vent in the basement of Titan TV, almost suffocated. Many blamed Serena for not coming forward with proof that Xander was dangerous earlier. Serena was ready to leave town.
On her way out, she tracked down Caroline to ask her to give a letter to Eric. Caroline refused. But, while she was leaving, she colapsed and had a stroke. Serena called the paramedics and got Caroline help in time. This move softened Eric's feelings toward her. While not ready to reconcile, he let go of his ander toward her. However, Nicole didn't. Nicole won a civil lawsuit against Serena for $250,000.
Upset by the lawsuit and her seemily hopeless love life, Serena went to Club TBD to drink. She met Chad DiMera there. The two drank most of the night together. They kissed. Chad wanted more and tried to take it further. Serena slapped him and walked out. Chad followed her. The next morning, she was found stangled to death outside of the town square. Chad was the main suspect.