Who is Joe in the novel, Gallowglass?

Joe, who speaks first, illustrates Vine's interest in the social misfits for whom Britain's National Health Service offers too little help too late. Raised by uncaring foster parents and ejected from a psychiatric ward by governmental cuts in welfare spending long before his depression is even alleviated, Joe comes close to throwing himself under an express train. He is rescued in the nick of time by Sandor, an enigmatic sadistic stranger with whom he falls into a selfless asexual love. Joe willingly becomes Sandor's gallowa glass, at his side each step of the tortuous way that Sandor plots to kidnap Nina Apsoland.