Reset ( TV story ) Reset was the sixth episode in the second series of " Torchwood " . It marked the return of Martha Jones to television after her departure from " Doctor Who " in " Last of the Time Lords " . It also marked the death of Owen Harper , starting a storyline that would feature prominently for the rest of the series . Synopsis . Martha Jones arrives at Torchwood after reports of numerous deaths . A medical researcher has been injecting workers with Mayflies . The Mayflies cure all illnesses before killing the patient , and Martha has got one . . . Plot . A series of seemingly - professional murder s in Cardiff prompt Jack to call in UNIT medical specialist Martha Jones for help . The Torchwood team are surprised and curious about Dr Jones ' relationship with Jack , as they still do not know much about his past . Martha informs him there have been similar murders throughout the UK . Owen and Jack flirt with her . Jack is more open and lighthearted when Martha arrives , dropping hints about their travels with the Tenth Doctor . When the two sit down for a brief catch - up , Jack tells Martha she should have contacted him if she was looking for work . Martha replies that she wasn ' t ; UNIT rang her out of the blue , and said she was what they needed , having been recommended by an " impeccable source " . Jack and Martha conclude it must have been the Doctor , as no one else knew about Martha ' s time - travel ling experiences . Jack says thoughtfully that perhaps the Doctor thought he owed Martha a favour . . . they all did , which makes Martha thoughtful . As the Torchwood team investigate the murders , they discover that one of the victims had been cured of diabetes and another of HIV . They trace the killings to a medical centre named the Pharm . One woman had been attacked but survived and is in a hospital . She has a seizure after admittance and fly - like creatures rise out of her mouth and try to enter Owen and Martha , but die first . Owen and Jack go to the Pharm and talk to the director , Professor Aaron Copley , but fail to gain access to any areas of the facility . After searching for ways of infiltrating the Pharm , the team learn the facility recruits people for human trials . Jack concludes it is far too dangerous to send one of their own undercover , but Martha suggests that if a doctor with the appropriate knowledge went in there , it would be less dangerous . After a verbal protest from Jack and a silent one from Owen , Martha convinces Jack to let her go in undercover as she ' s " been in worse situations " . Owen follows Jack and begs him not to let her go . Jack assures him he ' d rely on Martha if the world was ending . . . and he has . Ianto sets up Martha with her instructions and gear . A short conversation about his relationship with Jack ensues . Toshiko fits Martha with contact lenses that act as camera s , so the team can monitor her while she is inside . Martha goes undercover as Samantha Jones , a hepatitis sufferer , to investigate the centre ' s real purpose . Back at the Hub , Tosh and Owen are keeping watch over Martha in the Pharm . Tosh remarks upon seeing Owen gazing at the picture of Martha ' s UNIT badge , about their quickly developing friendship and that she and Owen are a perfect match , both of them being doctors . She points out Martha ' s obvious beauty and shares a laugh with Owen , who tries to feign ignorance . Owen remarks that the flirting is harmless , seeing that Martha is only interested in work and that if he tried anything , " Jack would have his kneecaps " . This seems to cheer Tosh up . Owen asks her about the pool tournament she was supposedly organising . Tosh says it was supposed to be a date . Owen looks abashed and asks Tosh if she is still interested . Tosh eagerly says yes . If they got to know each other outside of work , something could come of it , and Owen casually agrees to one date , which excites Toshiko immensely . He points out he wouldn ' t stop flirting with people just because of their situation and Tosh tells him that he can be " King Of Flirts " . The conversation disintegrates and they change topic and watch over Martha again . Inside the Pharm , Martha discovers the facility is responsible for the drug " Reset " , which is what cured the previously incurable diseases . The problem with Reset is that it works by releasing alien parasites called Mayflies into the human blood stream — the Mayfly larvae proceed to " reset " the human body , eliminating even incurable diseases like HIV . The downside to the drug is the Mayfly larvae eventually hatch and eat the person from the inside . Trying to escape , Martha is attacked by an adult Mayfly . She is captured by the Pharm workers who strap her to an operating table . The medical director examines her and states that her white blood cells have mutated due to " travel in time and space " . He questions Martha about her alliance with Torchwood and her travels . All the while , Martha acts as if she doesn ' t know what they are talking about . He is curious to see how her immune system will react to Reset and injects her with it . While Gwen and Ianto track down the Pharm - hired assassin carrying out the murders , arrest him and take him to the Hub , Jack and Owen find during questioning that he has a Mayfly in him as well . Jack needs the assassin alive so Owen tries to use the singularity scalpel to vaporise the Mayfly in his body . He screws up and the fly bursts out of the assassin ' s stomach instead . Toshiko concocts a program that will get them into the Pharm by controlling the car from the back while the dead assassin is strapped in the driver ' s seat . Inside the Pharm , the team split up : Tosh , Gwen and Ianto are sent to find the " research labs " , while Owen and Jack find the Director and Martha . Tosh , Gwen and Ianto discover the " labs " where alien life - forms are being held captive and tortured . By the time Jack and Owen reach Martha , the Reset drug has been injected and the Mayflies fight each other off until one remains inside . While Jack tells Prof . Copley that his team are shutting the Pharm down as a result of the damage they are doing , Owen tends to Martha , using the alien gun to extract the Mayfly from her body safely . The trio exit the Pharm before it reaches complete shut down and meet up with the other three by the vehicle they came in . Owen , who is supporting Martha as they walk , continues to flirt with her by suggesting she should spend a few days in bed , hopefully under his supervision . Martha says that she already has a boyfriend . Owen asks if he ' s ever saved her life like he just did . Martha replies that he has . As the team get ready to leave and Owen is ushering Martha towards the car , Professor Copley returns and points a gun at Martha , telling Jack and the others that he wouldn ' t just stand by and watch them ruin his work and let them get away with it . Owen steps carefully in front of Martha and attempts to reason with the Professor , claiming they are both rational men and that he doesn ' t really want to shoot . Professor Copley shoots Owen in the chest and Owen falls to the pavement in extreme pain , unable to even scream . Whatever mercy Jack was going to give the Professor is lost with this unforgivable act . Copley then points his gun directly in Martha ' s path and voices his intent to end her next , but the precious moment he wastes on a threat gives Jack a chance to shoot the Professor in the head , killing him instantly . Martha , Jack and Toshiko run to Owen , who lies on the ground , bleeding . While Martha gets out medical supplies , Jack holds Owen ' s hand and assures him he ' ll be all right , while Toshiko becomes hysterical . Martha and Jack try to get him to focus . Martha attempts to treat Owen ' s wound by injecting a medicine near his heart . Toshiko looks over him as a look of peace comes over Owen ' s face . Martha says that he is dead .