Written and directed by Anna Zlokovic, Appendage is a grotesque body horror film with a powerful message. It doesn’t take long to get started, with the film quickly introducing Hannah (Hadley Robinson), an up-and-coming fashion designer with a plethora of self-confidence issues, and the problem that arises after she is triggered by stress. Appendage has fantastic creature design and a layered, creative story that remains engaging even as its third act becomes a bit tedious.

Hannah is trying to get her designs into her boss’ spring show, and she’s under a lot of pressure to deliver a statement dress that is unique and will draw positive attention. In addition to a stressful job, Hannah has also been seeing her boyfriend (Brandon Mychal Smith) for six months and things are getting really serious between them. With so much on her plate, Hannah starts having pain on the site of her birthmark, and ultimately births a creature intent on preying on her biggest insecurities.

Appendage is apparent in its message — the creature that emerges from Hannah’s body is quite literally her self-doubt. It tries to wear her down in its attempts to make itself more powerful, and Hannah easily buys into the things it tells her because she has always believed them about herself. So insecure that Hannah begins to doubt her own friendship with best friend Esther (Kausar Mohammed), who the creature implies is in love with Hannah’s boyfriend. Hannah is haunted by the creature’s words and the film goes to show how easy it is to stand in one’s own way when the onslaught of self-doubt is so consistent.

There is always a reason not to do something or to avoid being happy because Hannah believes she shouldn’t be, and Appendage leans into how detrimental it can be to one’s mental health and personal relationships to feel that way. The film is also not under any impression that these things have a handy or quick solution, as insecurity doesn’t simply disappear overnight; the horror portrays it as a constant threat to one’s life and wellbeing. It’s certainly a strength of the film, as are the performances, which are committed and memorable.

Mohammed is especially a standout, showcasing her loyalty and love for her friend with a deep sincerity. She gives Esther a lot of life and energy, which helps to establish her and Hannah’s friendship. Emily Hampshire is always a delight, and she’s great at balancing the sweet with the creepy aspects of Claudia. Robinson has her work cut out for her, as she must convey Hannah’s internal struggles externally, and the actress does so with verve. Her role gets especially daunting in Appendage’s final act, and Robinson balances the change in her main role to great effect.

It’s the film’s final act, however, that doesn’t hold up to all that came before. The buildup is good, but the climax falls short of the previously established tension. Appendage begins to wane by the time it gets to its end, and that keeps the film from soaring to its full potential. The horror is suitably unsettling and disturbing, especially as the creature develops and grows into its own, but it’s ultimately the end where the story is a bit rushed and detracts from the overall intensity. All that said, Appendage is a solid outing by Zlokovic, and the horror elements complement the story’s message about self-doubt, even if it doesn’t push the envelope any more than it has to.

Appendage had its premiere at the 2023 SXSW Film Festival on March 11. The film is 94 minutes long and not yet rated. It will be released on Hulu at some point this year.