Question: does alex ever come back to law and order

Answer: Yes, In the season-six episode ``Ghost'', events surrounding the arrest of Liam Connors (Brian F. O'Byrne), the assassin who shot her, led to Cabot's return from the Witness Protection Program as Connors is arrested for her murder while being pursued for several others and an attempted murder of a young boy who witnessed one of his crimes. She reveals that the assumed identity she was given was an insurance salesperson originally from Tulsa, that she was living and working in Wisconsin under the name ``Emily'', and that she missed her mother's funeral in New York due to what happened. She is reluctant to see him convicted of a murder he did not commit (he does not know she is alive, either), but still wants justice and testifies against him in court. Connors goes to prison, having been found guilty under two counts of attempted murder (Cabot and an eight-year-old boy), plus five counts of murder. Upon winning the case, the SVU squad goes to Novak's office to celebrate, awaiting Cabot to join them. She does not show up, as the federal agent informs them that she has moved under a new identity and she asked him to say goodbye.