Shelby Van Pelt's novel pairs two unlikely protagonists: Tova, a seventy-year-old widow working night shifts at an aquarium, and Marcellus, the giant Pacific octopus who lives there. Tova is methodical and solitary, still grieving her son Erik who disappeared decades ago. Marcellus is intelligent and observant, with the octopus's prodigious memory and problem-solving abilities. When Marcellus discovers information about Erik's fate, he must find a way to communicate across the species barrier. Van Pelt alternates between Tova's perspective and Marcellus's, giving the octopus a distinctive narrative voice that is alien but sympathetic. The novel is both a mystery—what happened to Erik?—and a meditation on grief, connection, and the possibility of understanding between very different minds. Van Pelt researches octopus cognition carefully, grounding her imaginative leaps in real science. The book has been embraced by readers who find in Tova and Marcellus unlikely but moving companions. This is a gentle novel that takes seriously both the sorrows of human life and the mysteries of other consciousness.