Marcel is an adorable one-inch-tall shell who ekes out a colorful existence with his grandmother Connie and their pet lint, Alan. Once part of a sprawling community of shells, they now live alone as the sole survivors of a mysterious tragedy. But when a documentary filmmaker discovers them amongst the clutter of his Airbnb, the short film he posts online brings Marcel millions of passionate fans, as well as unprecedented dangers and a new hope at finding his long-lost family.