Finn Abernathy is a squintern at the Jeffersonian Institute first introduced in the episode The Hot Dog in the Competition in Season 7, he has returned in a recurring capacity since. Finn did not appear in season 10, the first season in which he is absent or is not mentioned, since his first appearance.
Abernathy is a sweet southern boy from North Carolina, who is trying to live without the shadow of his past haunting him. Various people in the Jeffersonian treated him badly upon learning of his criminal past but eventually treated him better upon learning that he just wants to put his past behind him and talk science in the lab. Upon telling Hodgins this, they eventually become friends - even going as far as to tease each other. He has only gotten upset once: when Hodgins used the last of Finn's hot sauce that his deceased grandmother had made, ignoring the note Finn had left stating that it belonged to him and without realising that the hot sauce had sentimental value. Finn forgave him after Hodgins used the lab equipment to discover the recipe and make more. He is a very honest person and has seen to have trouble lying, shown when his girlfriend, Michelle, visited him and requested he didn't tell her mother, Cam, but he told Cam anyway and tried to cover it up with Cam's help.
Finn had a criminal record with charges including joyriding, theft and attacking his stepfather with a hunting knife when he abused his mother and had spent some time in juvenile detention, but the record was expunged when he turned 18. Finn decided to quit, but he came back and received a warning from Brennan. After he returns to his work, Brennan asks him if his interest in forensic anthropology was related to a plan to kill his stepfather, to which he answered yes. She also asked him if he actually killed his stepfather, which he answered no because after reading a paper she had published, he knew there was no possible way to cover up the murder if he had actually committed it.
In "A Bump in the Road", he begins a relationship with Camille Saroyan's daughter, Michelle Welton. Cam initially disapproves, causing Finn to back off out of respect for his boss's wishes, citing that he owed her a great deal for giving him a second chance and that since she is Michelle's mother, he has to respect her wishes. Cam soon relents upon realizing they really want to date, and allowed the both of them to date. He attempts to lie when Michelle visits him without telling Cam she was coming but ends up blurting it out to Cam, Cam comes up with a plan where Finn would arrange to meet Michelle and then tell Cam where they were meeting so she could "accidentally" stumble upon them, pretending not to have known Michelle was in town. Afterwards Cam relents and tells Michelle about what happened, Michelle becomes upset and threatens to let Finn "have it", but Cam convinces Michelle to forgive him.
In The Turn in the Urn, Michelle breaks up with Finn because she realized she is still too young to commit to one person.
Finn originally doesn't get along with Jack Hodgins who teases him due to his southern accent and colloquialisms but Finn convinces him that as they both speak science they should focus on that not on what is different about them, Hodgins relents and they become friends after jointly making a snake vomit up evidence, even teasing each other in the form of nicknames, Hodgins calls Finn "Opie" and Finn calls Hodgins "Thurston". Finn has only gotten upset with Hodgins when he used the last of Finn's hot sauce that his deceased grandmother had made, ignoring the note Finn had left stating that it belonged to him and without realising that the hot sauce had sentimental value. Finn forgave him after Hodgins used the lab equipment to discover the recipe, using a swab from the bottle and making more after getting Finn to taste it and make sure it tasted like the sauce his grandmother made. Due to the nice taste, the two decide to enter into business together, getting a chef on their side to help make it and market it as "Opie and Thurston's Hot Sauce".
(Note: For those interested, the ingredients of the hot sauce are: red and yellow peppers, cayenne, tomatoes, garlic, onions, cumin, salt, brown sugar, vinegar, and Aframomum Melegueta, otherwise known as Guinea grain.)