We've seen only sporadic appearances by Caitlin O'Connell at the Denver Center for the past few years, so her return to play Lane, the achievement-obsessed doctor who hires a reluctant maid in The Clean House, was a joy. Beginning as a rigid perfectionist in an icy white suit, she evolved into someone far wilder and woollier as the play progressed. At one point, she was called upon to laugh until her laughter turned to tears. She turned this fairly common dramatic device into a revelation. There's something catlike and mysterious about O'Connell, something intriguing going on beneath the surface. Half the pleasure of watching her comes from trying to figure out what it is.