ILLUSTRATED by SUMMERS Frank Pembroke sat behind the desk of his shabby little office over Lemark's Liquors in downtown Los Angeles and waited for his first customer. He had been in business for a week and as yet had had no callers. Therefore, it was with a mingled sense of excitement and satisfaction that he greeted the tall, dark, smooth-faced figure that came up the stairs and into the office shortly before noon. "Good day, sir," said Pembroke with an amiable smile. "I see my advertisement ha