The Debate Society has got to be New York City's most charming theater company. The troupe's idiosyncratic nucleus is comprised of actor-playwrights Hannah Bos and Paul Thureen, who bring a delightful air of gentle whimsy to their peculiar little plays, which they've been staging with remarkable ingenuity under the direction of Oliver Butler for over a decade. On stage, Thureen and Bos's characters typically come across as disarmingly affable and kind, but always with a trace of arsenic seeping in somewhere around the edges. You want to eat them with spoon, only later realizing their sweetness conceals something caustic. So it is with Jacuzzi, their latest evocative dark comedy.

Lights up to reveal the comforting rustic interior of a Colorado ski chalet, circa 1991, where Bos and Thureen quietly read in the enviable comfort of a bubbling jacuzzi. Both seem enthralled by matching copies of a parenting book called Making Bobby Robert by Jackie and Robert Elder, the estranged couple who own the chalet. They're recently divorced, as we'll soon learn when Robert barrels into the scene, and their son Bobby has grown into an entitled mess of a man, in no small part because of all the psychological experiments they conducted on him for their book. Such as:

For one week we made sure to never laugh in front of Bobby. Anyone visiting our home wore cardboard masks, ensuring emotionally neutral expressions.

Creepy hot tub reading time is soon interrupted by a shivering Bobby, who's been coaxed back from his spoiled brat escapades in Switzerland to participate in a father-son ski race (daddy promised a cash infusion in exchange for some family bonding). Bobby, now in his early 20s and going by the handle "Bo," rumbles up in a snowmobile and appears resplendent in designer neon ski gear. Portrayed with boorish aplomb by Chris Lowell, Bo agrees to join the strangers in the new jacuzzi his father has installed, even though he doesn't really have a clue who they are.

Neither does the audience, for that matter, and a mysterious fog enshrouds Helene (Bos) and Derek (Thureen) throughout much of the 80-minute performance. Bo assumes they're renting the chalet, while his father (portrayed by Peter Friedman as a chipper cad) assumes they're the caretakers he's paying to pack up all the furnishings to be shipped back to his ex-wife. But both father and son are too blinded by their long-simmering resentments and disappointments to bother questioning the amicable couple who seem so understanding and eager to please. And when the hot tub feels this good, why dwell on what lurks beneath the bubbling surface?

Laura Jellinek's stunning set design is rendered in sumptuous hyper-detail, complete with a retro cassette stereo and TV/VCR, a pile of fluffy snow outside a sliding door, slanting wooden chalet ceilings, and of course the titular jacuzzi, where most of the play's subtle story unfolds. The understated narrative has the whiff of a '90s Hollywood thriller, but The Debate Society is too subversive to execute cliché plot points, and they're not interested in parodying them either. Instead, a liminal layer of dark menace, never fully articulated, hangs in the air throughout. It's a strange play, and you're never really sure where it's going, which is certainly preferable to the alternative.

The Debate Society is always at its best in ambiguity, as their aesthetic invites the audience's imagination to fill in deliberately open gaps, while they revel in the idiosyncrasies inherent in fraught situations. We're told that Bo has done some very bad things, but we never find out what they are. His father is an unscrupulous sybarite capable of writing a best-selling book about parenting but incapable of doing it himself. Helene and Derek are obviously not what they seem, but the real depths of their unsavoriness are, for most of Jacuzzi, only inferred. Even though the story never fully "pays off" in any conventional sense, the excellent ensemble keeps it afloat on the strength of their endearingly awkward characterizations.

"Is that weird?" asks Bo, stripping down to his skivvies as he prepares to join Helene and Derek in the jacuzzi, just moments after intruding on their vacation. Yes, that is, and it's for the best.

Jacuzzi continues through Saturday, November 8th at Ars Nova (511 West 54th Street)