The allegory is a bit confusing, but the message is still striking, thanks to Marielle Heller's surreal statement about all that is asked of mothers.

It's been more than half a century since Helen Reddy sang, "I am woman, hear me roar!" but the line remains as good a mantra as any for Amy Adams' ferocious lead role in Marielle Heller's tamer-than-expected "Nightbitch." Identified only as "Mother" in the credits, Adams plays a woman who gave up her career to raise her son but only now, four years into stay-at-home momhood, realizes how much the experience has changed her. "Transformed" might be a better word, since her ancient awakening gives off serious werewolf movie vibes. This mom believes she might be turning into a dog.

Novelist Rachel Yoder opens “Nightbitch” with the words “to my mother and to all mothers.” To some, that might sound like a warning—“male readers (and childless cat ladies) are not welcome here”—when in fact, the book has something to teach us all. Like Yoder’s book, Heller’s bitingly literal adaptation starts from the premise that motherhood is a primal instinct, a universal experience that bonds humans to other animals. But it’s also a strangely well-kept secret, forcing women to face its challenges alone.

While a thousand mommy bloggers and pregnancy book authors have dedicated their lives to demystifying the experience, “Nightbitch” speaks to all those mothers who missed the memo. That seems to be the case for Adams’ mother, who is understandably overwhelmed. As her lovable but not-so-attentive husband (Scoot McNairy) disappears for days at a time, she’s running herself ragged raising their son (blonde twins Arleigh Patrick Snowdon and Emmett James Snowdon take turns in the role).