The man in black fled across the desert, and the gunslinger followed.
Her red hair (fading to blonde at the roots) is tied back, to keep the strands from blowing into her face as she tracks the fallen shreds of Walter Bishop's suit. He can flee, but never far enough to outrun the disaster he has brought to both worlds.
Her partners are dead, her son is dead, her world is dying.
When Olivia Dunham finds him, she will remember her father's (Lincoln's, Charlie's, Henry's) face and aim with her eye, shoot with her mind, and kill with her heart.
At the start of the Dark Tower series, Roland the gunslinger is chasing a man named Walter across the desert. The "coincidence" (because all stories are the same story, aren't they?) was too much to pass up.