Motherhood is a brutal business for the title character of William Francis Hoffman’s “Cal in Camo,” an earnest and tenderhearted play about the search for family that opened Friday night at the Rattlestick Playwrights Theater. This conscientiously assembled production’s stark opening image presents a solitary woman locked in what appears to be mortal combat with a breast pump.

That woman turns out to be Cal, who has recently given birth to her first child, a daughter. And as played with angry bereavement and bewilderment by Katya Campbell, she is a vivid refutation of the idea that a mother bonds instantly with her newborn.

Mind you, Cal is starved for familial connection. But the little bundle of joylessness with which she occupies her days isn’t filling the bill. “Look at what your baby’s doing to me,” she snarls at her bone-tired husband, Tim (David Harbour, excellent), a beer salesman unhappily transplanted from his native Chicago to an isolated starter house in rural Illinois.

So Cal, who grew up mostly in foster homes, imports the only other living relative she knows exists: her brother, Flynt (Paul Wesley), a taciturn hunter from river country who has just lost his wife in a flood. Yes, this man of the woods seems to be a man of few words. But when he speaks, it is with the wisdom of someone whose calloused fingers are on the rhythmic pulse of Mother Nature.