"She was extraordinary," Sarah Delaney says of the young soldadera, a female revolutionary soldier, who stares confidently from a framed black and white photo that hangs in Sarah's home. Sarah, known as a "bit of a recluse," is famed for her photographs of the 1910-1920 Mexican Revolution. At ninety-one, she suddenly reaches out to Kayla Carlson and Abel Castellano of the Oral History Program at The University of Texas at El Paso, inviting them into her home to interview her about her life in the border city of El Paso, Texas, during the Mexican Revolution. Sarah explains, "You and I both have something to gain from reopening the past."

Through a series of interviews, Sarah reveals the drama, turmoil, violence, and heartache she experienced in El Paso during the Mexican Revolution. Witness to battle and execution, smuggling and sedition, internment and deportation, racial profiling and race rioting, Sarah shares the events and people—including historical figures such as Generals Francisco "Pancho" Villa and John J. Pershing—that remain woven into the fabric of her memories. Sarah undertakes the interviews in hopes of rewriting "the conclusion of her life."

Set against the backdrop of the Mexican Revolution, Light, Which Impresses examines the turmoil of that period and its impact on individuals living in the border region.