Who is Alex Morny from The High Window and what is their importance?

Alex Morny, a former actor, currently runs a fancy nightclub and gambling operation in an exclusive neighborhood. He hires Marlowe to investigate Vannier, who is having an affair with his wife. Morny believes Vannier is involved in criminal activity, and he wants him exposed. He later provides Marlowe with a valuable clue, a receipt to Vannier for dental supplies. Morny ultimately tries to frame his wife for Vannier's death.