Pip meets the convict in the marshes in a cemetery.
Pip’s meeting of the convict was a fortuitous event, for sure.
The day starts fairly ordinarily. Since most of Pip’s family is dead, including his mother, father, and many siblings, he is in the graveyard looking at their headstones. It is there that the convict finds him. The convict was running away, and still in irons. He sees the boy as an opportunity to get some food and a file to get rid of the chains, especially when he learns that Pip lives with a blacksmith. The convict threatens him repeatedly, and handles him a little roughly, but he does not really mistreat him.
Pip is still polite to the man, despite the situation. He even seems sympathetic.
At the same time, he hugged his shuddering body in both his arms - clasping himself, as if to hold himself together - and limped towards the low church wall. As I saw him go, picking his way among the nettles, and among the brambles that bound the green mounds … (Ch. 1)
The convict is cold, wet, and injured. Pip does not have much in his life, and is not used to people treating him generously or lovingly. His reaction to the man is to see through the brusqueness to the man’s innate goodness, such that it is. Pip’s politeness and kindness to the man shapes the rest of his life.
When Pip finally meets Magwitch under better circumstances, he is shocked to learn that it was Magwitch who funded his “great expectations.” To Pip he has been apprenticed to a criminal. He is ashamed and frightened of Magwitch. Yet as time goes on Pip learns to care about Magwitch like a second father, and risks his life to try to get him out of the country.