The Torchwood team is called to a building site where a human skeleton and an alien artifact have turned up. Owen (Burn Gorman) identifies the skeleton as a woman who died from a gunshot 200 years ago. They return to the Hub, where Tosh (Naoko Mori) is infuriated by Owen’s flirting with Gwen (Eve Myles). She retreats to a bar where she meets Mary (Daniela Denby-Ashe), who knows about Torchwood and claims to be a scavenger of alien artifacts. She gives Tosh a pendant that allows her to read minds. Tosh says she will not reveal where she got it.
The next day, she reads Owen’s and Gwen’s minds as they show contempt for her. She goes home and finds Mary there. Mary will not accept the return of the pendant, insisting it can be used for good. Tosh reads Mary’s mind and ends up spending the night with her. Mary says her real name is Philoctetes. The next day, wearing the pendant on a crowded street and trying to sort out the myriad thoughts about her, Tosh finds one man preparing to commit murder and stops him.
Owen reveals that he misread the skeleton and it was a man who died of trauma. Tosh asks Jack (John Barrowman) abut Philoctetes and Jack tells her about the archer who was exiled on Lemnos during the Trojan War. At home, Mary convinces Tosh to read the minds of the others at Torchwood to find out about the artifact discovered with the body. She finds she cannot read Jack’s mind at all. Owen reports that the same trauma that was visited upon the skeleton has been reported off and on for centuries. Jack becomes suspicious of Tosh’s strange behaviour.
Mary reveals herself to Tosh as an exiled dissident alien and the artifact can help her leave Earth. She refuses to allow Tosh to enlist the help of Torchwood but wants Tosh to take her there so she can retrieve the artifact herself. Jack has deduced that Mary is the murderer. The artifact is a transporter for a guard and a prisoner. Arriving on Earth in 1812, Mary killed her guard and began taking human form. Mary holds Tosh at knifepoint, demanding the artifact. Jack tells Tosh to hold still as he hands it over. When Mary takes it, she vanishes and Jack reveals he transported her to the centre of the Sun. Owen and Gwen apologize to Tosh, Tosh destroys the mind-reading pendant, and she tells Jack that she was unable to read his mind, as if he was a dead man.
Owen and Tosh compare the wound on the skeleton to the death of John Hurt in Alien. When Tosh reads Ianto’s mind, she finds him tormented about his girlfriend’s death. Mary appears to be an Arcateenian and her transformation into one of the creatures is startling and beautiful. At this point in the series, seven episodes in, every main character has kissed someone of the same sex. Clearly, Russell T. Davies is not afraid of such scenes and the BBC is no longer squeamish.