Supergirl, also known as Kara Danvers, was sitting in her living room when her son, Alex, ran up to her with an excited grin. He had just woken up from an afternoon nap and couldn't wait to share his dream with her.

"Mom, I had a dream where I was a superhero like Superman, and I even defeated Supergirl!" Alex exclaimed, his eyes shining with excitement. Kara couldn't help but smile at her son's enthusiasm.

Kara decided to play along with her son's dream. "Oh really, little man? And how did you manage to defeat Supergirl?" she asked, ruffling his hair affectionately.

"I had this green rock! It made Supergirl weak!" Alex said, running off to his room. He returned with a familiar glowing green rock. Kara's smile faded as she recognized it as Kryptonite.

Her heart pounded in her chest. How did Alex get his hands on Kryptonite? And worse, he didn't know she was Supergirl. She was in a dangerous situation.

Despite her fear, Kara continued to play along. "Where did you find this rock, Alex?" she asked, trying to keep her voice steady.

"I found it in the park," Alex answered, unaware of his mother's discomfort. "It looked cool, so I brought it home."

Kara knew she had to get the Kryptonite away from Alex. She also knew she had to explain why, and that meant revealing her secret identity.

She took a deep breath and said, "Alex, I need to tell you something important. But you have to promise to keep it a secret."

Alex looked at her with wide eyes. "I promise, mom," he said. His innocent trust gave her the strength she needed to reveal the truth.

"I am Supergirl," she said softly. Alex's eyes grew even wider. "And this rock, it's dangerous to me. It's called Kryptonite."

There was a long silence as Alex processed what his mother had just revealed. Then, he hugged her tightly. "I won't let the Kryptonite hurt you, mom," he said.

Kara was relieved. She knew that Alex was too young to fully understand, but she was glad that he was willing to protect her.

Together, they safely disposed of the Kryptonite. Kara explained to Alex the importance of not picking up strange objects and the dangers of Kryptonite.

That night, as she tucked Alex into bed, he asked, "Mom, are you really Supergirl?" Kara smiled and nodded, "Yes, Alex, I really am."

"That's so cool!" Alex exclaimed, his eyes lighting up. "But don't worry, mom. I won't tell anyone. Not even dad." His words warmed Kara's heart.

From then on, Alex became Kara's little protector. He promised to always keep her secret safe and to never bring home strange rocks again.

Supergirl's secret was safe, and so was she. And perhaps, for the first time, she felt that her double life as Kara Danvers and Supergirl was truly worth it.

Alex's dream had unknowingly brought danger, but it also brought them closer. Mother and son, they understood each other better. They had a secret, a bond that was now stronger than ever.

Kara knew that she had made the right choice. Her son's safety was her priority. And in revealing her secret, she had not only saved herself but also strengthened her bond with Alex.

And every night, before Alex went to sleep, he would look at his mom and say, "Goodnight, Supergirl." And Kara would reply, "Goodnight, my little superhero."

Their secret brought a new dimension to their relationship. A secret they both cherished. A secret that made their bond unbreakable. A secret that gave them strength and courage.

In the end, Kara realized that being Supergirl was not just about saving the world. It was also about being a mom, protecting her son, and teaching him the values of truth, justice, and love.

And while the world knew her as Supergirl, to Alex, she was simply mom. The bravest, most amazing mom. A mom who was also a superhero.

And so, life continued for Supergirl and her little protector. Together, they faced each day with courage, love, and a secret that made them stronger.