 In his first appearance , John Hart is as a rogue Time Agent and former partner of the series ' lead male character Jack Harkness ( John Barrowman ) both professionally and sexually . Whilst the original function of the Time Agency — stated to have ceased operation by the time Hart appears — is left unspecified , John 's own backstory is briefly given , as well as having had a relationship with Jack he has been in rehab for an addiction to alcohol , drugs , sex and murder . John leaves earth disgraced after his initial self @-@ interested plot is foiled by Harkness ' Torchwood team , though returns in the series finale " Exit Wounds " where he is eventually given a chance to redeem himself . 
