What does the ending show?

In the school's production of The Forest, Aarav had been given the part of Tree Number Three. Tree Number Three had no lines. He stood at the back of the stage in a brown costume with cardboard branches, and his only job was not to move.

Aarav was very good at not moving. He had practised in front of the mirror, arms out, until his shoulders ached.

On the night, halfway through the second act, the boy playing the Woodcutter forgot his lines. He stood in the middle of the stage with his wooden axe, staring at the audience, and the silence grew longer and longer.

Aarav knew every line in the play. He had heard them all at rehearsal, night after night, with nothing to do but listen.

So Tree Number Three leaned forward, very slightly, and whispered: "I have walked for three days and found no water."

The Woodcutter blinked, repeated the line, and the play went on.

Nobody in the audience noticed. But at the end, when the actors took their bows, the Woodcutter took Aarav by his cardboard branch and pulled him to the front of the stage. And the teacher, who had noticed everything, clapped loudest of all.