- "There are two pressurized water reactors, thirteen miles north of here. The cooling system failed in one. The reactor melted down last year, killing a lot of people who were trying to keep it humming."
- —Grace tells Alicia and Morgan about the plant.[src]
At some point before the outbreak, the power plant was built to withstand terrorists and had enough supplies to keep the staff alive for months. It had two pressurized water reactors.
As the apocalypse began to unravel, Grace, an operations manager at the plant, called in all of the shifts to keep the plant running. As things gradually worsened, she called in all of their families to join them. As the world came to an end and the cities fell, people no longer required the power the plant provided, but Grace chose not to evacuate. Instead, Grace turned the plant into a safe-zone for survivors, taking advantage of the supplies and the plants sturdy construction which would keep out the dead.
However, the survivors lacked the infrastructure to keep the plant running correctly and the cooling system in one of the reactors failed. The reactor melted down, killing everyone inside the plant and irradiating the surrounding area. Grace returned to the plant in an attempt to find survivors and spent days looking but couldn't find anyone. In the process, Grace was exposed to a lethal dose of radiation despite taking precautions.
A year later, Grace had established roadblocks and fences warning of high radiation levels to keep people out of the area around the plant that would be lethal to the living. The survivors who had perished during the meltdown became radioactive walkers, dangerous to anyone living who encountered them. Grace worked to hunt down the radioactive walkers and bury them in some caverns near the plant where their remains couldn't contaminate anyone living.
After capturing and forming an alliance with Althea, Isabelle explains that while on a supply run with her partner Beckett, they saw the plant and the aftermath of the meltdown. Seeing that and the radioactive walkers drove Beckett insane with the fear that he would end up like them, forcing Isabelle to kill him.
As Morgan's group works to repair their plane, Grace contacts them and reveals that the plant's second reactor is in danger of melting down. If it occurs, everyone in the area will die from the radiation that'll be released. Grace enacts a plan using the truck stop's generator to buy some time, but she expects that the reactor will melt down regardless of their actions to prevent it from doing so.
Grace returns to the plant with the generator, but overloads it trying to power the cooling system. Grace predicts that they have only twelve to twenty-four hours at most before the second meltdown. After rescuing Strand and Charlie, Morgan, having found another radiation suit, comes to Grace's aid. Together, the two manage to repair the generator. However, that night, alarms go off at the plant, drawing in walkers. Grace confirms that the alarms mean that the second meltdown is beginning.
The next morning, the alarms continue to sound and Grace warns that when the alarms stop is when they need to start worrying. Chased by a herd, Grace decides to lead it to the roadblock and use the alarms to draw the herd to the power plant. However, the alarms stop as the containment building finally fails. The second reactor melts down, leaving a cloud of radioactive dust blowing into the air, visible for miles around. Morgan's group manages to escape on the repaired plane they flew in on, narrowly avoiding flying through the radioactive cloud.
- Although never named in dialogue, the plant's name can be seen on a parking permit that Morgan finds in the car of one of the workers in "Still Standing".
- The credits for "Still Standing" features the power plant with one of the reactor towers spilling smoke into the air, presumably foreshadowing or representing the coming meltdown.
- The name Lonestar Power & Light reflects its purpose and location in Texas which is known as the Lonestar State.