Based on the bestselling novel, writer and teacher Iris (Naomi Watts) finds her comfortable, solitary New York life thrown into disarray after her closest friend and mentor (Bill Murray) bequeaths her his beloved Great Dane, Apollo. The regal yet intractable dog immediately creates practical problems for Iris, from furniture destruction to eviction notices, as well as more existential ones. Yet as Iris finds herself unexpectedly bonding with Apollo, she begins to come to terms with her past, and her own creative inner life in this story of healing, love, and friendship.