Arnold Wesker is a minor character in Batman: The Telltale Series. An inmate of the ailing Arkham Asylum, he was one of the inmates that Bruce Wayne can interact with whilst committed to the facility.
Not much is known about Arnold Wesker before he was committed to Arkham Asylum. However, he seemed to be a skilled ventriloquist and may have been tied to the profession before he was committed. Arrested for an unspecified crime and diagnosed with Dissociative Personality Disorder, he was committed to Arkham Asylum in the hopes that he would receive the care that he needed.
However, it seemed that staying there only made his condition worse, to the point in which he used a sock as a puppet to represent his aggressive personality. It seems that Arnold was also bullied by some of the other inmates, which made his recovery harder. He also grew scared of some of the other inmates, including "John Doe". It is implied that he might have fallen to the key prank that John would often play on new inmates.
When Bruce Wayne was committed to Arkham Asylum by Mayor Dent, he first saw Arnold in the Recreation room and was advised to stay away from him by John. However, Bruce can interact with him and "Socko", asking them about John, a key that John gave him or complement his skill. When John caused a riot by cutting Zsasz, Arnold would only watch as the serial killer fought the orderlies and possibly Bruce Wayne.
When the Children of Arkham took over Arkham, Arnold was among the inmates seen during the preparations to release them. It is unknown what he did when they were released, but it's possible he either took part in the riots or remained in his cell whilst the other inmates ran amok. Regardless, he was likely to have been one of the many inmates rounded up by both staff and the GCPD, and returned to his cell.
Arnold seemed to be a meek individual, acting timidly around others. He seemed to prefer being on his own and rarely interacted with others. However, Socko, who he controlled and used to project his other personality, was rude and aggressive towards others, often telling them to go away when they interacted with either of them. It seems that Socko had a grasp over Arnold and that he would be the only one who interacted with others.