The play begins with a disembodied head, tastefully parked in the middle of a table, amiably conversing with some sort of technician - in what could be a Samuel Beckett play or the sci-fi film The Brain That Wouldn't Die.

But that isn't InterAct Theatre's style. No, this was the latest new work by resident playwright Thomas Gibbons (Permanent Collection, etc.) titled Uncanny Valley - an important exploration of the technological possibilities of immortality. It opened Wednesday at the Adrienne, traveling similar territory as Caryl Churchill's A Number (about cloning) and the Tod Machover opera Death and the Powers (in which a rich industrialist downloads himself into his possessions), but going farther than both.

The head in question has adult intelligence but little knowledge, much awareness but no experience. He's a sweet, neutral personality. The technician is actually an esoteric researcher helping to assemble an artificial body - no Frankenstein-esque horror here - with both parties enjoying the mutual companionship. If the visual image of a body under construction was not so odd, such scenes might be dull.

As the head acquires limbs and the exaltation of animation - some trimming is warranted here as those scenes are variations on the same character dynamics - we learn he's a lifelike android receiving the download of his existence: The personality of a cancer-riddled billionaire.

Social-ethics issues surface, and some of the best writing arrestingly describes the experience of trading bodies (it's like leaving a collapsing building) and the sexual possibilities of inhabiting an artificial body. But that's not the point. This delicate, ingenious play is about identity. Are we who we say we are? Or who we're told we are? Both, though the heartiest put stock in the former rather than the latter.

Both characters have children accusing them of moderately questionable child-rearing behavior. Is that one of the memories the billionaire selectively left behind in the creation of his new self? Or has his son had too many sessions with therapists specializing in "found memories"? They'll see each other in court. The researcher's daughter sounds like she's been brainwashed by a religious cult. But unlike with the billionaire, the suffering has been profound. Might the constructive and destructive power of words be greater than any futuristic technology?

The well-investigated production directed by Seth Rozin walks as many fine lines as the script. At first, I wondered whether Sally Mercer was too unscarred to be a retirement-age researcher. But while maintaining ultra-professional restraint, Mercer somehow ages before our eyes as her sorrows multiply. Frank X delivers a masterful metamorphosis from cipher to worldly billionaire with hugely resourceful use of vocal color. But his hallmark is where words stop and implication begins. How many actors so eloquently think on stage?

Uncanny Valley

Through April 26 at InterAct Theatre Company at the Adrienne, 2030 Sansom St. Tickets: $22-38. Information: 215-568-8079 www.InterActTheatre.org.EndText