Pip meets the escaped convict very abruptly early in Chapter I. The location is near the sea south of London by perhaps twenty miles.
Ours was the marsh country, down by the river, within, as the river wound, twenty miles of the sea.
Pip is ten years old at the time. He is an orphan. He is visiting the graves of his father, mother, and five dead siblings in the churchyard. Dickens does not explain how such a large family all came to be deceased. He only mentions that the children's graves were
...five little stone lozenges, each about a foot and a half long, which were arranged in a neat row beside their grave, and were sacred to the memory of five little brothers of mine - who gave up trying to get a living, exceedingly early in that universal struggle...
Pip is feeling sorry for himself. He might not have met the convict who was hiding among the grave stones in the cemetery if he hadn't started crying. Then the convict feels compelled to intervene. His unexpected materialization from out of nowhere only adds to the terror inspired by his wild-animal-like appearance and his savage threats.
"Hold your noise!" cried a terrible voice, as a man started up from among the graves at the side of the church porch. "Keep still, you little devil, or I’ll cut your throat!"
When Pip explains that he lives with his sister and her husband Joe Gargary the blacksmith, the convict gets the idea of using the terrified boy for two purposes--to bring him some food and to bring him one of the blacksmith's files. This is to be the most significant meeting in Pip's life. When he brings the food and the file the next morning, as recorded in Chapter 3, the convict is so grateful that he remembers it for many years. Pip was so frightened of having his heart and liver torn out and eaten, as the convict threatened if he disobeyed, that he brought an overabundance of food, including a half-bottle of warming brandy and a whole pork pie.
Pip doesn't see the convict again until Chapter 39 of the novel. The convict, whose name turns out to be Abel Magwitch, risks hanging by breaking the law and returning to England from exile in Australia. He does this specifically to see Pip, whom he has secretly made a gentleman through sending the riches he has acquired in Australia to the lawyer Mr. Jaggers to act as Pip's guardian. Pip, who is now twenty-three years old, has actually become a fastidious London gentleman and is horrified to learn that his unknown benefactor was not Miss Havisham but the escaped convict he met on the marshes.
"Yes, Pip, dear boy, I’ve made a gentleman on you! It’s me wot has done it! I swore that time, sure as ever I earned a guinea, that guinea should go to you. I swore arterwards, sure as ever I spec’lated and got rich, you should get rich. I lived rough, that you should live smooth; I worked hard, that you should be above work. What odds, dear boy? Do I tell it, fur you to feel a obligation? Not a bit. I tell it, fur you to know as that there hunted dunghill dog wot you kep life in, got his head so high that he could make a gentleman - and, Pip, you’re him!"