When offender profiler Black investigates several deaths on a cargo ship, he encounters a mysterious woman who shows him visions of a life in which he had never joined the Millennium Group.
Frank Black (Lance Henriksen) is an offender profiler working for a private investigative firm called the Millennium Group, who consult with local or federal law enforcement on criminal cases.
Stymied, Black and fellow Group member Lara Means (Kristen Cloke) investigate the ship, finding several bodies hidden in a crate, all having died of exposure.
However, they all agree that after she boarded, crew were discovered daily, dead of exposure on the ship's bow; Law had the woman chained up in the belief she was responsible.
Black visits "Lee" at the hospital, where she speaks to him in perfect English, discussing personal events from his life of which she would have no knowledge.
Black seeks out Lee in a refugee camp; meanwhile, Law and his crewmen are also tracking her, conspiring to kill her to avenge their fellow crew.
She compared its central premise to the film It's A Wonderful Life, and considered this a common trope in television; VanDerWerff also felt that the plot structure, with a supernatural event being encountered during a criminal investigation, was overly reminiscent of Millennium's sister show The X-Files.
[7] Robert Shearman and Lars Pearson, in their book Wanting to Believe: A Critical Guide to The X-Files, Millennium & The Lone Gunmen, rated "Siren" three stars out of five.
Shearman compared the episode to "The Curse of Frank Black" and "Midnight of the Century", though finding that the immigration plot left it less focused and interesting than those installments.