What is Gatsby doing when Nick first sees him?
While we, as readers, and Nick, as the narrator, are provided with some information about Gatsby earlier, the first time Nick sees Gatsby is at the end of Chapter One. Gatsby is Nick's neighbor, and as Nick returns to his new home after his visit at the Buchanans', he sits outside before going into the house "on an abandoned grass roller in the yard" (25). He turns his head to watch a cat moving in the moonlight, and it is then he gets his first glimpse of Gatsby, a mere fifty feet away. He sees that,
[A] figure had emerged from the shadow...and was standing with his hands in his pockets regarding the silver pepper of the stars (25).
Nick knows that Gatsby is the person who owns the mansion next door to him, and he concludes from the man's stance, which seems proprietary, that this is Gatsby.
Nick decides to call out to Gatsby to introduce himself, but changes his mind because,
[He] gave a sudden intimation that he was content to be alone - he stretched out his arms toward the dark water in a curious way, and as far as I was from him, I could have sworn he was trembling" (25-26).
All that Nick sees that Gatsby could be watching and stretching his arms toward is
[A] single green light, minute and far away, that might have been the end of a dock" (26).
Gatsby then vanishes into the shadows and Nick must wait to meet his mysterious neighbor.
Thus our knowledge of Gatsby builds indirectly and gradually. We know very early that Gatsby had,
[A]n extraordinary gift for hope, a romantic readiness such as I have never found in any other person.... (6).
We hear again of Gatsby from Jordan Baker when she and Nick are visiting the Buchanans, when Jordan tells Nick he "must" know Gatsby, implying that everyone knows Gatsby, and we observe Daisy's odd response to this, restating the name and asking "What Gatsby?" (15) in a demanding way. At dinner, there is no further talk about Gatsby because Daisy has a bit of a meltdown when Tom is called away from the table with a phone call from his mistress. So we are tantalized by what we do know and further tantalized by Nick's first glimpse of Gatsby, a solitary figure who seems to be yearning for a green light across the water.