Niki is the ingenue of Curtains, an odd combination of murder mystery, farce and heartfelt tribute to musical theater. In the role, Erica Sweany was charming throughout, long-limbed and graceful, with a lovely singing voice. In the Arvada Center production, she really got to strut her stuff in a gorgeous Rogers-and-Astaire-style duet with Jim Poulos called "A Tough Act to Follow," a number that provided such pure, dizzy pleasure, you wanted it never to stop.