Isobel ('played' by Hannah Murray) is one of last suriviors of the Etheri, a powerful civilisation all but wiped out during the Time War. She was saved by a unimaginably powerful being called Meshinkio (the creator of the Reapers) who placed her undercover as a human student at Skullmoor school. In return, she was intended to faciliate foiling the Apocalypse Chaser's plot. Allowing Meshinkio to seperate the two timelines.
Following her introduction in Claws of Time Captain Jack insisted Isobel be detained at Torchwood in order to moniter he suitability for human society. As Isobel had just began a romantic relationship with Craig, this enforced seperation was a cause of angst for both.
In Black Swan the nature of tbe Etheri was revealled (Isobel was unawere as this infomation is only given to Etheri at maturity) An Etheri body is actually a shell containing three independant beings. In Isobel's case the evil and awesomely powerful Black Swan and the benign goddess White Swan. Jack intended to kill Isobel in order to protect the world from the Black Swan, Gwen, Ianto, along with Kyle and Craig rebelled against this. However following the revelation that Craig's love could repress the Black Swan, Isobel was allowed to leave the hub and join Operation Delta.
Isobel is kind, sensitive and often naive to the ways of modern human society making her appear a little fragile and twee at times. She loves nature and tends to see the beauty in everything around her. She enjoys painting, and playing the harp and is currently attending sixth form college alongside Craig where she has made some new friends and had to deal with the possiblity of the Black Swan remerging.