Malcolm Sloan was the secret lover of Evelyn Marsh who lived in the Marsh home, acting as Evelyn's brother and family driver.
During an episode of abuse, Malcolm went to James and told him that he swore he would kill Marsh.
He observed James and Evelyn having a romantic encounter the following day.
Later in the evening, he went to Evelyn and kissed her.
After Jeffrey was killed, Malcolm and Evelyn pinned the blame on James, though they were the ones responsible.
Finding James and Evelyn in an embrace, he hit James with a gun and prepared a cover story, framing James again as having come back to kill her, and her killing him in self-defense.
He tried to convince Evelyn to leave her fingerprints on his gun so he could then kill James, but she refused. James' friend then burst into the home, pleading for James' life. Malcolm then commanded Evelyn to hand over the gun, but she shot Malcolm, killing him.