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Unknown alien fled from the Sorvix' God to Cardiff at the time, when Torchwood Three was rebuilt by Gwen Cooper. She took over her body and posed as Gwen for a couple of months, raising only slight suspicion that "something was off" from Jack Harkness and Mr Colchester. (AUDIO: Herald of the Dawn)

She killed Gwen's mother (AUDIO: Aliens & Sex & Chips & Gravy) and other individuals, who suspected that she wasn't who she seemed to be. (AUDIO: Tagged) While posessed, the real Gwen's consciousness unsuccessfully tried to communicate with the others. Only the alien could hear her. (AUDIO: Aliens & Sex & Chips & Gravy)

While investigating an escape room with Rhys, Mr Colchester and his husband, she raised more suspicions from Colchester for her ruff decisions. (AUDIO: Escape Room, Herald of the Dawn) Eventually Andy Davidson contacted Jack, when "Gwen" started to behave strangely upon hearing the proclamations "God is returning" from random people. Jack faced "Gwen" at the Hub, where Mr Colchester tried to contain the unstable Rift. Jack asked him to leave it as it is, and burst of energy from the Rift separated real Gwen from the alien. (AUDIO: Herald of the Dawn)