Plot summary
Jack, Owen, and Gwen, pursue Bernie Harris, a petty thief carrying something emitting an alien signal in his jacket, through the Cardiff streets. Gwen chases Bernie into a train station, and is able to grab his jacket but he gets out of it and runs away. Gwen discovers an alien device in the jacket pocket, and when she activates it, she sees a vision of a lost boy called Tom Flanagan wandering the train station in 1941.
Torchwood try to find Bernie in Splott. Unsuccessful, they return to the train station to try the device again when Owen activates it while under a bridge. He witnesses Ed Morgan rape and murder Lizzie Lewis in 1963. In the Hub, Toshiko investigates the crime to confirm what Owen saw, and finds that no one was charged for Lizzie's murder. The Hub's computer analyses that the nanotechnology of the "quantum transducer" allows people to see moments of the past spurred by strong human emotions.
Owen confronts the elderly Ed on his own but gets no information out of him; however, upon leaving his house, he spots Bernie and takes Bernie to a pub to learn more about the device while the rest of Torchwood is en route. Bernie explains he found the device in a tin of random objects from an old lady, and that he too saw the murder of Lizzie, and wonders if the team wants the "other half". Torchwood follows Bernie back to Bernie's home to retrieve the other half as well as the other alien objects. Bernie explains that he only used the other half once, as it showed him bleeding to death outside his home at his current age. As they leave, Gwen accidentally triggers the second half, and has a vision of herself holding a bloody knife, calling out to Owen.
Torchwood realise that Ed is being blackmailed by Bernie; Jack becomes concerned that Owen may have triggered Ed to take action. Learning that Ed has left his home and is heading towards Bernie's, Owen disarms Ed and takes his knife. Determined not to let Ed get away with his crime, he decides to avenge Lizzie's death. He is stopped by Gwen, who takes his knife. Ed runs and impales himself on his own knife. Gwen sees that this is the future she saw. Jack locks the device away.
Credits
Adapted from Wikipedia contributors, Ghost Machine (Torchwood). Narrative and paragraph formatting adjusted; illustrations, reference markers and non-story material omitted.