From inside, she pulled the chunk of concrete that had been lodged in Denise's head. Her shoes, her purse, the drops she had used that day for her allergies. Their mother sat by and cried while the girls sat spellbound and listened.
"She felt we needed to know," says Kimberly, "because it was a part of us, too."
But it wouldn't be until their parents were interviewed by Spike Lee for his Academy Award-nominated 1997 documentary, "4 Little Girls," that the McNair sisters fully understood. Everything their parents had kept to themselves came out. As Kimberly puts it, the film made Denise "three-dimensional." Their father would travel to different cities to attend the film's premieres and sob at every one of them. It was, they believe, the purge he'd so desperately needed. Now, whenever the sisters see the film, they start crying as soon as the opening credits roll.
Their mother, Maxine, was in the church's choir loft when the bomb exploded. She jumped up to try to find her daughter, not knowing she was buried in the rubble. She wouldn't see Denise again until, at the hospital, she and her husband later identified their only child's lifeless body.
"I couldn't stop screaming for several days," Maxine says. "They had to give me an injection to calm my nerves."
The couple, who had tried to have more children ever since Denise was born, came home to silence.
That they had another daughter almost exactly a year later, and then another, felt like a miracle.
Today, Lisa and Kimberly look at their mother with awe and admiration.
"No one would have blamed her if she'd crawled into bed and cried for the rest of her life," says Lisa. "Mama said a minister friend of hers told her, 'Maxine, God has a divine plan, and you just have to follow it.'"
As an evening summer storm pounds the living-room skylights in the Birmingham-area home the family shares, their rescue dog Banjo vies for lap space.
Maxine, now 85 and suffering from Alzheimer's, swats the mutt away -- "Get that thing on the floor." She closes her eyes but never stops listening. As the conversation turns to what Denise might have been, Maxine's eyes open.
"She would have been awesome," says Lisa, who remembers stories of Denise standing up for others. "A doctor or lawyer or politician."
"I think she would have left Birmingham. I just think she would have been adventurous," says Kimberly. "And I'm sure she would have given my parents the grandchildren they wanted."
"We have granddogs," says Lisa, giving Banjo a squeeze.
"You two are crazy!" Maxine howls with laughter.
Her face then turns serious for a minute as she reflects on her firstborn, a child she lost 50 years ago and one she does not forget, even as her mind fades.
"She wasn't going to let the world pass her by."
Her other daughters came of age in a time unlike Denise's. Their world was more integrated. They reaped the benefits of their sister's sacrifice.
Kimberly McNair Brock is now married, 44, and serves as their mother's primary caretaker. She's also a chef focused on holistic nutrition.
Lisa, 48, is single and works for a nonprofit that uses animals to help people heal.
While they didn't feel they had to live their lives for the sister they lost, Kimberly says she felt like she was born without anonymity -- and with eyes trained on her.
"People knew about me before I got here," she says. "You were already measured before anyone gave you an opportunity to be who you were."
She also says she has gravitated to women about 17 years her senior, the same age Denise would have been if she was still alive -- an unconscious effort to fill a void.
The sisters feel a duty to honor Denise's legacy. They participate in Sojourn to the Past, a program that teaches high school students about the civil rights movement. They are also active in a scholarship fund established in the four girls' memory -- "giving people the chance to do what they couldn't," says Lisa.
What's more, they know it's on them to speak.