Hitch is an agent of Spectrum who comes to work for Ruby's family under the cover of a "house manager" (though he is more commonly referred to as a "butler") so he can watch and assist Ruby while she works for Spectrum- he was assigned to this as he was "out of action" due to a gunshot wound (the doing of Nine Lives). It is revealed that he is 42 in the last book (Blink and You Die). He is also Ruby's "sidekick" (according to Ruby) and very good friend.
As for his appearance, not much has been mentioned apart from the fact that he is considered to be quite attractive. Sabina, Ruby and Consuela are mentioned in the first book to have noticed (Consuela is not mentioned directly in the book to have noticed but at one point is seen giggling with him in the kitchen).
Throughout the series, Hitch rescues Ruby from danger that she recklessly puts herself in.
Hitch is one of the top agents at Spectrum 8 even before Bradley Baker "died" in a plane crash. At first Ruby is reluctant to trust Hitch, and is suspicious of his intentions, thinking he was a gangster/hit man/bozo/goon after seeing the gunshot wound on his arm.
In the first book (Look into my Eyes), Hitch appears at the door of the Redforts, claiming that he had come because the couple he served previously ("The Wellingfords") were ''off riding elephants in India.'' Ruby, however, did not believe him and knew that he was up to something. She then realises after joining Spectrum that Hitch is in fact an agent who is currently working undercover as a house manager to protect Ruby on orders from Spectrum.
His care for Ruby grows through out the book, and when he finds that when Ruby was kidnapped he is extremely worried and is shown to have been slightly angry when he sees Ruby being dragged along the corridor by Baby Face Marshal as he points his gun silently towards him.
In the final book (Ruby Redfort: Blink and you Die) Ruby breaks into the secret files and it is revealed that Hitch's real name is Art Hitchen Zachery who, along with Bradley Baker, was a victim of attempted murder by a JSRP (junior space recruitment program) agent who's name was Casey Morgan otherwise known as Buzz.