At the heart of Wendy Kesselman’s unnerving drama My Sister in This House reside some disturbing questions about human nature. Based on a ghastly crime committed in a French village in the early 1930s, the play speculates on the conditions that led two live-in housekeepers, sisters known for having docile dispositions, to brutally murder their employer, a bourgeois, middle-aged woman, and her teenage daughter. Steadily ratcheting up the tension, Kesselman develops a troubling profile of unraveling minds, both in the mother and daughter who live in callous insouciance to any matters outside their class concerns, and the two sisters whose isolated attic quarters have exacerbated their alienation from the outside world. The imposed detachment of the sisters’ existence gives rise to a desperate codependency in which increasingly violent fantasies become harder to repress with each indignation. Kesselman’s narrative runs on an anxiety amplified by inevitability. Mounted by Theatre Pro Rata under the seasoned direction of Carin Bratlie Wethern, My Sister provocatively asserts the perils of a stagnant social order that forsakes the slightest recognition of common humanity.