Chad Hartigan’s “Little Fish” is set amid a pandemic. Not the one we’re currently living through, but one that raises many more existential questions. Instead of Covid-19, the film’s fictional world is suffering from NIA (neuroinflammatory affliction), which causes a mysterious, mass memory loss.

Hartigan (“Morris From America”) and the screenwriter Mattson Tomlin tell the story of a newlywed couple, Emma (Olivia Cooke) and Jude (Jack O’Connell), while jumping timelines before and after NIA, including their engagement in the fish section of a pet store. The film may be shortsighted about the global scope of this disease, but the microcosmic focus allows for a much more emotionally devastating film.

Once you’re swept up in Emma and Jude’s romance — it’s not hard, even though the montages veer a little too precious — the skimmed-over science matters little. This is sci-fi rooted more in feelings than fact. Its resonance is similar to “Eternal Sunshine of the Spotless Mind” though it’s arguably antithetical in plot.

The weight of the epidemic is felt through Emma and Jude’s small social circle. First, their couple friends Ben and Samantha are affected (Raúl Castillo and the singer Soko, who contributed to the soundtrack). Then Emma’s mother learns she has it. But the real gut-punch lands when Jude’s memory starts to fade. “They say you can’t forget feelings,” Emma says. But what happens when one party has no recollection of the past that led to falling in love? And if memories shape one’s identity, what does it mean for Emma to continue loving someone who is no longer his original self? The answers are not all there, but the questions keep the film intriguing.

Little Fish
Not rated. Running time: 1 hour 41 minutes. In theaters and on Google Play, Vudu and other streaming platforms and pay TV operators. Please consult the guidelines outlined by the Centers for Disease Control and Prevention before watching movies inside theaters.