Kosher Lutherans centers on Hanna and Franklyn, the seemingly perfect couple who desperately want to have a child of their own, but are unable to do so. As the couple begins to wonder if they'll ever become parents, they have a chance encounter with a God-fearing pregnant girl from Iowa who offers to let the couple adopt her out-of-wedlock baby.
Just before the adoption papers are signed, Hanna and Franklyn discover the girl is unaware that they are Jewish. Knowing the revelation could throw a ratchet into the whole works, the couple poses as Lutherans to appeal to the girl's apparent Midwestern sensibilities. But how far are they willing to go to have a family?