A corporal in the Military Assault Command Operations detachment assigned to Enterprise for its mission into the Delphic Expanse, serving under Major Hayes.
Corporal McKenzie joins the ship with the rest of the MACO team in The Expanse and The Xindi, and is seen through the third season as one of the handful of soldiers regularly given names and lines.
In The Xindi she is part of the squad that goes down to the trellium mine to bring out Archer and Tucker, the first demonstration of what the MACOs can do. She goes on to take part in boarding actions and in the guarding of prisoners and sensitive areas of the ship during the search for the Xindi weapon.
Like the rest of the detachment she answers to Hayes rather than to Reed's security staff, an arrangement that causes friction between the two officers for much of the mission.