Ars Nova is one of those intimate, creatively flexible venues, like the Soho Rep, where you never know what to expect when you enter the space. This is, after all, where a Russian-themed cabaret environment was created for Natasha, Pierre and the Great Comet of 1812, and where a burlesque theater was imagined for Eager to Lose. With the Debate Society’s production of Hannah Bos and Paul Thureen’s Jacuzzi, a sometimes humorous, sometimes tense suspense drama with a faint whiff of Emlyn Williams’s Night Must Fall, the audience is placed in three rows of (uncomfortable) bentwood chairs along one long wall. Only a few inches away on the other long wall is the realistically detailed interior—designed by Laura Jellinek—of a ski chalet high in the Colorado mountains. The wide, narrow room, with sliding doors to the snowy exterior at stage right, is dominated by a practical hot tub used so extensively you’ll feel yourself getting pruney. Bradley King’s lighting creates shimmering reflections of the hot tub’s water on the wood-beamed ceiling. A period-perfect TV figures in the action and puts an accurate time stamp on the plot about to unfold.