Finding himself on the streets and with a young sister to look out for, Gunn trades his soul for a a truck which he turns into a vamp fighting machine.
Living hand to mouth he, his sister and his crew of homesless kids do the best they can, which is pretty good, to keep the vamps at bay.
Spotting Angel in his vampiric form threatening a man who is black mailing a client, Gunn vows to stop him. Although he puts on a good show, he does not succeed but his efforts gain Angel's respect and also his concern for the kids welfare.
A gang war between Gunn's crew and a local nest of vampires leads to Gunn's sister, Allonnah, being kidnapped and vamped. When Gunn tracks her down, he has to kill her, but Angel turns up to stop the blood bath that would have ensued. He eventually gains Gunn's respect and Gunn then continues to help Angel and soon becomes a fully fledged member of Angel Investigation.
Becoming more and more involved with Angel Investigations and believing that Angel has got the 'mission', Gunn gradually leaves his crew behind and starts to see the grey between the black and white of good and evil.
When the team bring back Fred from Pylea, Gunn falls for the kooky large-brained Texan and the two become sweethearts. Although he breaks up with her when the demon he sold his soul to comes back for payment, it was only to save her from pain and, once Angel has killed the bad guys, they get back together.
Despite his former reservations about the vampire and his fast freindship with Wesley, Gunn sticks by Angel, during Wesley's absence from the team due to his betrayal of Angel and ends up running Angel Investigations and searching for Angel together with Fred when the rest of the crew have dissappeared.
When Fred runs into her old professor only to find that he was the one that sent her to Pylea, Gunn murders the proffessor to save Fred from doing it and him from losing her. However, his actions cause them to grow apart and they eventually separate.
Gunn is the only person up for the challenge when the Senior Partner's offer Angel Infistigations the LA Branch of Wolfram and Hart on a plate. While there he is offered the chance to have a brain enhancement that will enable him to be a kick ass lawyer, and also have knowledge of the entire works of Gilbert and Sullivann. Gunn jumps at the chance to at last be more than just the brawn and feels that he has at last become a useful member of the team.
Everything has it's consequences though and when he starts to lose his knowledge he agrees to sanction the release a package from customs in return for making the enhancement permamnent. Little did he know at the time that his actions would lead to Fred's death and her body being taken over by an ancient demon, Illyria.
Full or remorse and wanting to atone, Gunn exchanges places with Lindsey McDonald in a Wolfram & Hart holding dimension where he must have his heart ripped out by a demon every day. He is ultimately rescued by Illyria, the demon who he unwittingly helped to take over the body of Fred.
With the final battle near at hand, Gunn agrees to help Angel in the battle and once again gets to do what he does best, vamp fighting. He survives his battle to face the coming wrath of the Senior Partner's together with Angel.....
