With the help of his grandmother Connie and their pet lint, Alan, Marcel, an endearing one-inch-tall shell, scrapes by in a vibrant world. They are the lone survivors of an unexplained disaster and were formerly a part of a vast community of shells. However, a documentary filmmaker finds them hidden among the junk in his Airbnb, and when he puts the short film online, it attracts millions of ardent admirers, as well as fresh threats and hope for Marcel to find his long-lost family.