When struggling filmmaker Dean (writer-director Dean Fleischer Camp) moves into an Airbnb, he quickly discovers that he is not alone. Marcel (Jenny Slate), an adorable one-inch-tall shell, already lives there with his grandmother Connie (Isabella Rossellini) and their pet lint, Alan. Once part of a sprawling community of shells, Marcel and Connie live alone as the sole survivors of a mysterious tragedy. Taken with his unlikely new friend, Dean starts filming Marcel and his grandmother, igniting a meteoric rise to internet fame that changes their lives forever. But will Marcel's newfound sense of possibility and a throng of superfans be enough to track down his long-lost family?