A riot raged in the La Mesa Prison in Tijuana, Mexico. Thousands of inmates battled the guards with bottles and rocks, while the guards shot back with machine guns—until a small American woman in her 70s walked into the middle of the war, raised her hands, and signaled for quiet. Remarkably, calm fell on the prison.

That woman was Mary Brenner, who was raised in Beverly Hills. There she lived what she called "a glamorous life," until she found Christ and followed him in a whole new direction.

Now she's known as Sister Antonia. She dresses in a nun's habit and lives in a sparse 10-foot cell inside the prison. She moved there 25 years ago to live among murderers, thieves, and drug dealers. Sister Antonia has poured out her life for these prisoners, nursing their wounds, getting them eyeglasses and medicine, caring for their families, and washing their bodies for burial.

Loving them doesn't mean she ignores their crimes. In her words, "There isn't anyone who hasn't heard my lecture. They have to accept that they're wrong. They have to see the consequences. They have to feel the agony…but I do love them dearly." She refers to each prisoner as her son.

Although she lives in a prison, the prison does not live inside of her. Her friends and the inmates all describe her incredible energy, joy, and hopefulness. She describes it as simply living out her calling. In a recent interview she said, "I wouldn't trade this cell for any place in the world."

Update – Editor’s Note: Sister Antonia died in 2013 at the age of 86. She had ministered to the prisoners for more than three decades.