"The Testament of Mary" (directed by Deborah Warner, at the Walter Kerr) is theatre porn. Stiff with its own seriousness, it's a Broadway show that wants to impress us with its anti-Broadway intellectualism, while straining for a big, tricked-out success. The ninety-minute monologue, adapted by Colm Tóibín from his 2012 short novel, is a story about torture, stoicism, and mortification in extremis. It imagines the authors of the Gospels solemnly grinding away at the mother of Christ for insights into her son, while she questions whether Jesus was fathered by God at all. Tóibín's Mary (Fiona Shaw) shuns attention, or, at least, a particular kind of attention. She will not allow these zealots to construct a sanctified Pietà out of her family's blood and complications. Instead, she composes her own Gospel, addressing the audience directly as she races about the stage, using various props - a shroud, large nails - to illustrate the play's ultimate scene of horror: the Crucifixion. Mary treats her son's death less as a source of grief than as an occasion to reveal the chasm between his followers" belief in his immortality and her own skepticism. Her description of Jesus" martyrdom might work better at the beginning of the play, where it would ground us in the familiar narrative before Mary begins to rewrite or, rather, claim it. Shaw displays her fabled savagery and strength in the role. Like the brilliant monologuists Ruth Draper and Lily Tomlin, she has a real commitment to the text - as well as a susceptibility to its weaknesses. But is someone else's language enough for Shaw? Like too many actors known for their solo work, she is taken with the phenomenon of her own art. Part of the reason she works so hard as Mary - in a portrayal that, in the end, feels hard - is to convince us that Tóibín's lyrical style is worth competing with. Shaw is the kind of performer who is often treated as the "author" of her characters. But Tóibín's creation is a willed one - his Mary is more idea than flesh, and Shaw has to push and push to find Mary's credibility as a character. Time and again, she turns the mother of Christ into your typically crusty and sage Irish mother, whose tone of certainty and self-pity reminds one of W. B. Yeats's poem "Song of the Old Mother": "I rise in the dawn, and I kneel and blow / Till the seed of the fire flicker and glow / And then I must scrub and bake and sweep / Till stars are beginning to blink and peep." . . .