A lion was sleeping under a tree when a mouse ran across his paw.
The lion woke up, caught the mouse in one swift movement, and held him up to look at him. The mouse was very small. Smaller than anything the lion usually bothered with.
"Please," said the mouse. "Let me go. I am too small to be worth eating. And one day - maybe - I will help you."
The lion looked at the mouse for a moment. Then he laughed. The idea of this tiny creature helping him was genuinely funny. He put the mouse down and went back to sleep.
The mouse ran.
Some weeks later the lion was crossing the far side of the forest when he walked into a hunter's net. It had been spread between three trees, nearly invisible, and by the time he felt it he was already tangled. He pulled and twisted and roared but the more he struggled the tighter it held.
He roared for a long time. The forest heard him.
So did the mouse.

He came quickly, found the net, and began to chew. Not at the thick ropes - those were too much - but at the smaller threads that held everything together. One by one. It took a while.
The net came apart.
The lion stood up, shook himself, and looked at the mouse.
The mouse looked back.
Neither of them said anything. There was not much to say that the situation had not already said.
No creature is too small to matter. And kindness given without expectation has a way of finding its way back.