The original convict learns that Pip has seen another convict on the marshes.
To avoid confusion, let’s call the original convict Magwitch. On the way to bring Magwitch food, Pip runs into another convict. This one is younger, but also cold and frightened. He tries to hit at Pip, but ends up running away. When Pip suggests that he cannot get any more food for the second convict, Magwitch thinks nothing of it until Pip says he looked like he needed food.
Magwitch is surprised that Pip has seen the other convict. He is frightened and scared. Pip describes the convict, dressed the same as Magwitch, and notes that he had a “badly bruised face” (p. 16). Magwitch is infuriated when he realizes who it is.
“Where is he?” He crammed what little food was left, into the breast of his grey jacket. “Show me the way he went. I'll pull him down, like a bloodhound. Curse this iron on my sore leg! Give us hold of the file, boy.” (ch 3, p. 16)
Pip points, and Magwitch runs after the other convict. We do not learn until later the strange story behind these events, and the betrayal of Magwitch by Compeyson. At the time, Pip assumes the second convict is with his convict, whom he later learns is named Magwitch.