Ballet and modern dance are two entirely different worlds in form and function, so the idea of staking out one's career between the realms could well be an invitation to madness. But Robin Stiehm isn't living on the verge of an artistic split-personality disorder. In fact, the choreographer embraces her dual (and dueling) dance forms, having spent 20 years in the ranks of Loyce Houlton's Minnesota Dance Theatre, and the New Dance Ensemble and Lab. What that means on the stage is that she employs her rigorous ballet training to create progressive movement as lyrical as it is physically demanding. What really surprises people about Stiehm, however, is that the woman's quiet demeanor seems to mask an intriguingly dark imagination that manifests itself in absorbing dances filled with treachery, deceit, and disturbing visions. Shades of Edward Gorey's Victorian parlor games colored last year's "Circus Subterfugium," while the mean-spirited "Give/Get/Take" followed the prototypical love triangle to extremes. Stiehm wisely balances her taste for the lurid with a lighter touch, giving shape to group efforts that pour across the stage like sunshine from a window whose heavy velvet curtains have been thrown open.