The Vacillating Vigilante. The Hot Dog Detective (A Denver Detective Cozy Mystery), #22

There's a vigilante on the loose. He's killing people who have escaped justice or are in the process of committing heinous crimes. Former Denver detective Mark MacFarland thinks the police are going after the wrong suspects, but he is as much in the dark as they are. He is more interested in finding out who robbed a local bank and killed an innocent bystander when the robber attempted to escape. His interest in the case is piqued, however, when a former detective, Wally McCabe, asks MacFarland to find the killer of the innocent bystander.
"She was a friend, " says Wally. "I want justice for her."But when the bank robber is captured, he claims that the Vigilante Killer caught up with him, but for some strange reason, allowed him to live. Now it's time for MacFarland to find out who the Vigilante Killer really is. This cozy private investigator novel can be read an independent mystery book or as part of The Hot Dog Detective series.