Jack is a polite and composed individual, often exhibiting a butler-like attitude in his interactions with others. Beneath his formal exterior, he has a humorous and mischievous side, frequently teasing those around him, such as Sebastian Moran. Despite his lightheartedness, Jack remains deeply loyal to William and the group’s mission, carrying out his duties with seriousness when required.

He is also shown to have a flirtatious and bold streak. Jack quickly took interest when he learned that Irene Adler had joined their group, and even after discovering that Bond identifies as a man, he unabashedly offered to assist him with private “studies,” demonstrating his playful and shameless approach to social interactions.

Jack is a very tall man, standing at 6’6″ (198 cm), with a distinctive appearance marked by his goatee and long gray hair, which he typically ties back into a ponytail. In flashbacks depicting his first encounter with the Moriarty brothers, Jack is shown with shorter hair that was predominantly black, featuring only a few streaks of silver.

When he is first introduced, Jack wears a black waistcoat paired with a white kerchief around his neck. After officially becoming part of the Moriarty household, his attire shifts to a formal black three-piece suit, complemented by a black tie and a white pocket square.

Jack served in the British Army during the First Afghan War, where he earned the nickname “Jack,” referencing a pocketknife for his versatility and effectiveness. During his time in the military, he also worked as a combat instructor, passing on his extensive knowledge of melee fighting. His exceptional skills eventually led to him being infamously known as “Jack the Ripper,” a title highlighting his prowess in close-quarters combat.

Following the fire at the Moriarty household, William, Albert, and Louis James Moriarty were taken in by Lord Rockwell. At that time, Jack was employed as a butler in Rockwell’s estate. Aware of Jack’s past, the Moriarty brothers sought him out to teach them the techniques of combat and the art of assassination, skills that would later become instrumental in their pursuit of revolution.

William James Moriarty
Jack holds deep respect and loyalty toward William, following his leadership and aiding him in the execution of their shared plans. Having trained William in combat and assassination during his youth, Jack continues to support him wholeheartedly as part of the Moriarty group.

Albert James Moriarty
Jack served as a mentor figure to Albert, instructing him alongside his brothers in combat techniques. Their relationship is built on mutual trust, and Jack recognizes Albert’s critical role in the organization’s structure.

Louis James Moriarty
Like with William and Albert, Jack trained Louis in the art of combat. He treats Louis with a sense of protective familiarity, stemming from their early association at Lord Rockwell’s estate.

Sebastian Moran
Jack and Moran share a lighthearted, teasing dynamic. Jack often jokes with Moran, showing a more casual side of himself, though both maintain mutual respect as skilled operatives under William’s leadership.

Irene Adler / Bond
Jack displays flirtatious behavior toward Irene, and later toward Bond, even after learning of Bond’s true identity. His shameless and humorous attitude characterizes his interactions with them, contrasting with the otherwise serious atmosphere of the group.