Answer: The "malevolent phantom" is Boo Radley himself. Boo was locked away because he became a troublemaker, but the children believe he was monstrous or was killed.
Explanation: Scout compares Boo Radley to a ghost or a phantom. Boo Radley was locked in the house as a teenager because he was unstable and involved with a group of troublemakers and the family did not want him to go to jail. Then, when he was 33 years old, Boo stabbed his father in the leg with scissors. He was arrested, sent to jail, and once again released to the Radley’s custody—and never seen again. Jem said this, "There was a long jagged scar that ran across his face; what teeth he had were yellow and rotten; his eyes popped, and he drooled most of the time" (Lee 10), which characterizes Boo as a monster. "Maybe he died and they stuffed him up the chimney" (Lee 27) is another rumor.
