In "The Case of the Spanish Cross," Perry tracks down a frightened young man wrongly accused and on the run for grand theft and murder. In his hiding place, Perry asks the boy to trust him to help, with his first promise to turn him in to the police. With nothing but his word to depend on, the boy steps out with Perry in the seemingly forlorn hope that the lawyer will help him. At that, Perry puts his arm around the boy in appreciation of his trust, and we know this innocent young man will have the services of one of the greatest lawyers in fiction to defend him because of it.
Meta-example: When Raymond Burr was first approached about reprising his role for Perry Mason Returns, he gladly accepted, on one condition: that Barbara Hale be brought back as Della Street.