Little Fish is about Tracy Heart, a former heroin addict who is desperately trying to escape her past and achieve her goals and dreams. Tracy lives with her mother and brother in the Little Saigon area in Sydney, where heroin is readily available. She is in need of money to become a partner in the video store that she works in, but her loan applications are repeatedly rejected by finance providers, as a result of her past criminal record, poor repayments of credit card debt, history of drug use and lack of collateral. Tracy lies to both her mother and her boss at the video store, pretending she has received the loan. This is one of the recurring themes of the movie, the casual ways people lie to each other for convenience. Tracy is trying to help her drug addicted stepfather and former NRL star Lionel to kick his heroin addiction. After a four-year absence in Vancouver, her former boyfriend Jonny Nguyen, also a former heroin addict, has come back into her life. Jonny, who now dresses in business suits, claims to have employment as a stockbroker at a large firm and suggests he may be able to obtain the money Tracy desires through share trading. The romance between Tracy and Jonny is rekindled. Upon visiting Jonny's alleged workplace, Tracy discovers Jonny has lied to her and is not in fact employed as a stockbroker. Jonny has become involved in a drug deal with her brother Ray, and Tracy also chooses to become involved in the deal as she sees this as the only means of providing the finance she needs to become a partner in the video store. Tracy, Ray and Jonny set out to execute the deal, which ends in tragedy. Tracy's courage and deep love for those she cares about are notable in the climactic scenes of the film.
Little Fish received positive reviews from critics. The film has an 89% rating on Rotten Tomatoes based on 27 reviews. Metacritic assigned the film a weighted average score of 77, based on 9 critics, indicating "generally favorable reviews". Critics admired the film for its screenplay and the actors' performances. The critic Liz Braun said "Little Fish has beautifully understated performances and a script that emphasizes the mundane and the manipulative in the addict's world." Owen Gleiberman from Entertainment Weekly praised it mostly for its acting performances, saying "The actors are terrific, especially Weaving, who plays bottoming out as a tragedy spiked with gallows humor, and Blanchett, who digs deep into the booby-trapped nature of recovery. The revelation, however, is Rowan Woods, a major filmmaker in the making."