In 1812 Cardiff, a prostitute named Mary is fleeing a murderous soldier when she comes upon an eerie light. In the present day, the same woman watches as Torchwood arrives at a building site where an ancient cadaver and an alien device have been uncovered. Meanwhile, Tosh's unrequited attraction to Owen has left her feeling isolated from her teammates. When Mary approaches her at a bar, Tosh is relieved to have someone to talk to -- and then intrigued when Mary gives her a pendant which lets her hear people's thoughts. Now Tosh must grapple with the seductive power... and with the mystery of Mary's true motives.