A former soldier, Mary suffers from Disassociative Identity Disorder (DID). She has at least two different personalities: "Mary", who claims that she's from Wisconsin and is a sketch artist. When Mary is exposed to a variety of environment triggers, including cold or the sound of running water, she reverts to "Walker", a hardened assassin. They each know of the other's existence, but have little memory of what their other self has done.
As Walker, Mary Walker is a skilled fighter who uses a garrotte, drugs, and a machete in battle.
