In his younger days, Walter Simmons filled his life with adventure, exploring the fantastic and the unknown alongside his longtime friend Theodore Joseph Wells. Although he describes himself as a man of reason, this particular trait only extends as far as preferring to think his way out of situations rather than resort to violence; when it comes to seeking explanations for the mysteries he and Wells encounter in their adventures, "reason" does not often enter into Simmons's thought processes, and he will willingly embrace the supernatural and otherworldly as an answer. Indeed, it is this openness and eagerness that causes Wells to fear for Simmons's well-being, as it seems all too possible for him to be consumed by the terrifying and wonderful worlds and possibilities that their discoveries have opened up to him.
Putting his life of adventure behind him, Simmons became one of the First Seven, the founders of the organization which would become Sector Seven. He has lived long enough to remain in a position of power with the organization for the majority of its existence, becoming known and feared by many. It is said he knows where most of the skeletons are buried, and how they became skeletons in the first place. Those within Sector Seven refer to him as "The Old Man", but likely never to his face.
Walter is the father of Margaret Simmons, grandfather of Bill Simmons, and great-grandfather of Seymour Simmons.