Johnson (Children of Earth: Day One)

Dedicated enforcer for the Government who has been assigned the job of dealing with Torchwood at the start of the 456 crisis. Ruthless and efficient, she has little time for social niceties and is determined to see her job done efficiently and successfully. After knocking out Captain Jack Harkness, she used a laser cutter to get something out of him, not yet seen. After she told Dr Rupesh Patanjali that he couldn't go away and live freely, he realised that Captain Jack Harkness would kill him so he ran off and Johnson killed him. Judging by her technology (e.g, her laser cutter) she is not a 21st Century citizen.