Playing a real-life diva is no walk in the park, especially when your model is opera diva assoluta Maria Callas. But we'd go anywhere with Celeste Roberts after her spellbinding performance in Terrence McNally's bit of open-heart surgery, Master Class. Without singing a note, Roberts conjured the very voice of Callas: attitude, star quality, insufferable ego and gigantic insecurities. As she drilled her hapless trio of students in the fine art of singing — when she permitted them a moment to perform — Roberts opened up Callas's private world that once included incredible fame, her brutish lover Aristotle Onassis, her nemesis Jacqueline Kennedy and her rival singers (although to be fair, there were no singers who could touch Callas). Roberts gave us the heartache without sentimentality, the talent behind the ego and the woman behind the myth. It's a tour de force role, full of earthy fire and bursts of volcanic temperament, and Roberts (one of Houston's finest artists) sailed into the stratosphere like a shooting star.