That’s by design: the show, which premiered in London in 2010, concerns a deaf man and his hearing family, and interrogates the ways in which they communicate with one another. A great deal of the play is relayed through sign language, which punctuates the emotional highs and lows of the story with an emphatic, expressive, and often poetic punch.

What’s more salient, though, and part of Raine’s main argument throughout “Tribes,” is the ways in which words – spoken, signed, implied – fail us, and how language can never quite capture the anguish of our fundamental psychological traumas. It’s when these people don’t have anything to say – when the moment leaves them at a loss for words – that “Tribes” reveals its most potent truths.

Billy (Dave Wantuck, exceptional) was born deaf, and raised by hearing parents Christopher (David Marciniak) and Beth (Margaret Massman), alongside hearing siblings Daniel (Johnny Barden) and Ruth (Anna Krempholtz). When “Tribes” begins, Billy has just returned to the family home from university. His siblings are home, too: Ruth after attempting to make it as a singer, and Daniel licking his wounds from a recent breakup.

This is a group of navel-gazing narcissists, but their penchant for colorful arguments make them a blast to hang out with. The father is an academic and a critic who hurls clever insults around in shows of superiority and affection. His wife, a would-be detective novelist, smooths over her husband’s improprieties with a misguided motherly warmth. Siblings Daniel and Ruth bicker and spar about his dead-in-the-water thesis paper (about the insufficiencies of language, go figure), and her current, half-hearted foray into opera.

Between the barrages, they all find time to connect with Billy, who is spared from the intricacies of their verbal violence because of his deafness. He never learned sign language – his father all but insisted on this – which leaves him sometimes unharmed, but nonetheless adrift within the family hierarchy. (At one point, he describes himself as their “mascot,” beloved but not so much respected.)

When Billy meets Sylvia (a dazzling Melinda Capeles), a woman born to deaf parents who is progressively losing her hearing, he discovers both love and sign language. In the deaf community, Billy finally finds the ability to express himself beyond the confines of his cloistered family unit, and “Tribes” is mostly about Billy’s self-actualization as an adult with a full emotional range.

But part of what makes Raine’s play so brilliant and devastating is the ways in which she explores the fallout of Billy’s awakening within the family. Daniel, for instance, is slowly revealed to be a co-dependent mess, dealing with an array of mental health problems and a stammer returning from childhood, who would rather see Billy unhappy than lose his brother to the outside world.

Technically, this a gorgeous production. The set by Lynne Koscielniak is an exquisitely detailed London home, packed to the brim with the bric-a-brac of the cultural elite, with patches of the walls extending upward and doubling as screens for the supertitles during sign-language bits. The sound design by Katie Menke, so important in this show that emphasizes the musicality of our lives, subtly teases out emotion, and in key moments, invites the audience to understand the world from Billy’s perspective.

Director Doug Zschiegner uses all these elements to highlight and elevate the excellent work by this truly superlative cast. There is no shortage of outstanding moments, but special praise must be reserved for Wantuck as Billy. His journey is expertly performed, and a furious monologue delivered in the second act, where he asserts his independence and demands respect from his family, is a thrilling feat. It’s among the best moments of theater I’ve seen in ages, and it left me, fittingly so, without words.

Review

"Tribes"

4 stars (out of 4)

Presented by Road Less Traveled Productions through March 27 at Road Less Traveled Theater, 456 Main St. Performances are 7:30 p.m. Thursdays through Saturdays, 2 p.m. Sundays. An ASL show, with Deaf Access Services, is 2 p.m. March 27. Explicit language and profanity; must be 17 and older to attend. Tickets are $42 (roadlesstraveledproductions.org, 629-3069).