Lexi was Detective Alvin Olinsky's daughter. In Emotional Proximity, she died from injuries from a warehouse fire she was in. Alvin wanted Lexi to also be a detective like him but she wanted to go into music.

Season 1

Alvin and Meredith were having problems so Alvin began living in their garage. Lexi was very close with her father. She was suspended from school after they found drugs in her locker. Alvin was furious and later found out she was covering for her boyfriend. Alvin threatened him and told him to break up with her. Lexi was angered but understood where he was coming from.

In her suspension she was unable to go to the school's father-daughter dance, but she put on the dress anyway and the two did the dance in their back garden.

Season 4

Michelle was introduced as Alvin's estranged daughter who he began to get close with and finally told Meredith and Lexi about. Lexi wasn't happy about it.

Later on, in Death Trap, firehouse 51 responded to a warehouse fire. CPD were also at the scene and Alvin found out that Lexi was inside too, even though she wasn't supposed to be. Alvin begs Boden to go back in to find her after they left. Boden is indecisive as it's extremely dangerous but gives in to Alvin and sends a team back in. They save more teenagers and Lexi with it.

In Emotional Proximity, Dr Halstead told Alvin that they tried as best as they could but Lexi had too much internal damage from the fire as well as third-degree burns across most of her body. She is on oxygen and has isn't expected to last much longer. Meredith and Alvin sit by her bedside and hold her tightly while her mother cried and Lexi died.

The arsonist was caught and arrested in Chicago Justice's pilot episode, Fake.