From the Story
"Justin Finch-Fletchley is a first-year Hufflepuff."
Discovered in Book 2, Chapter 11, The Diversion
"After the attack on Mrs Norris, Justin starts avoiding Harry; he turns and walks the other way when he sees him. Harry later surmises that this is because he suspects that Harry is the heir of Slytherin.
During the Duelling Club, Draco Malfoy conjures a snake that looks as though it is about to attack Justin. Harry tells the snake to back down, without realising that he is speaking Parseltongue. Justin seems to believe that this is evidence that Harry is Slytherin’s heir and begins to avoid him. Shortly thereafter Justin is Petrified."
Discovered in Book 2, Chapter 14, Cornelius Fudge (chapter)
"Justin is Petrified along with Nearly Headless Nick and is cared for by Madam Pomfrey in the hospital wing."