Task: Question Answering
Input (English): Passage: Charles Spotswoode's son Jimmy became involved with "the Canary", a conniving showgirl. The Canary, determined to force Jimmy to marry her so she can join the social elite, threatens to reveal that Jimmy was embezzling from his father. She turns down the elder Spotswoode's bribe to leave Jimmy alone. She telephones two men she has been blackmailing, Cleaver and Mannix, and demands one final generous gift from each of them by the next day. She makes the same request of "creepy" admirer Dr. Lindquist. Her ex-husband Tony Sheel eavesdrops and wants half, but she refuses to give him anything, even after he hits her. Cleaver, Mannix and Lindquist are all shown lurking about her apartment building late that night.
Spotswoode visits her at her apartment around midnight, but cannot get her to change her mind. After he reaches the lobby of her building, he and another person hear screams from her place. They knock on the door, but she assures them that she is fine.
The Canary is found strangled the next day. The coroner places the time of death around midnight. District Attorney Markham investigates, aided by Philo Vance (a close friend of Charles Spotswoode) and Police Sergeant Heath. After all the suspects are brought in for questioning, Vance asks Markham to keep them waiting for a few hours. Markham agrees. Vance subtly maneuvers Cleaver, Mannix, Lindquist and the two Spotswoodes into playing poker to pass the time so he can observe their personality traits. Only one shows the daring, imagination and discipline required for the crime; that man bluffs Vance, betting everything with just a pair of deuces. The suspects are then released.
Sheel, who witnessed the murder while hiding in the closet, sends the killer several blackmail letters. He too is strangled. A pen found at the scene has Jimmy's name on it, so Heath arrests him for the murder. Jimmy then confesses to both murders, but Vance knows better. 
Question: What is the nickname of the person who has been blackmailing someone?
Output (English): The Canary.