The saint of the title is one Ted Crowther, who lives in a fairly new block of flats known as Concrete Canyon. He has earned his title because of his good works on behalf of the tenants. A little boy, Billy Darby, goes missing from the flats because he believes he is going to lose his pet hamster, as the Council won't allow pets in the flats. Crowther naturally is right there with the police to help look for Billy. But Crowther also runs a Savings Club for the tenants and this attracts the interest of DI Todd. (thetvdb.com)