Catfish follows the story of Nev, a young photographer who lives with his brother Ariel and friend Henry Joost in New York City. When eight-year-old artist Abby Pierce sends Nev a painting of one of his photographs, they form a friendship online via Facebook.
It isn’t long before Nev notices she has a good looking older sister Megan who is a dancer and songwriter and lives in Michigan.
Nev’s brother Ariel and roommate Henry, decide they want to make a documentary that follows Nev’s new online relationship with Megan, and it isn’t long before they talk about meeting up.
When Nev realizes that the music Megan has been recording has taken from YouTube and isn’t original, it doesn’t take him long to work out that Megan and Abby have made other false claims.
Ariel pleads with Nev to continue the relationship for the sake of their new film. Nev agrees, but it doesn’t take long before the three of them head to Michigan to confront Megan.
When they arrive, they head over to Angela’s house. On the drive over to Abby’s house, Angela says she has cancer and is going to start a round of chemotherapy soon. But when they get to Abby’s house she says “you’re confusing me,” as Nev asks her about her art.
When Nev wakes up the next morning, he has received a message from Megan saying she is unable to meet him because she is checking into rehab. Upset, Nev sits down for a serious chat with Angela, but she breaks down and admits she made the whole story up. She tells Nev that Megan is a friend of a friend, when in fact, the pictures of Megan are real of an independent woman in Washington.
Unable to stop telling lies, Angela claims that her real daughter Megan is in rehab and she has been estranged from the family for a long time.