There's just no telling what some kids will drag home with them.

Ricky, Ruthie and Ron Taylor are three siblings who come across an usual find, deep in a cave: an almost albino being that seems to be part boy, part bat. Once provoked, the creature bites Ruthie, so the siblings decide to take the bat boy back to their town to be put down by the local veterinarian, Dr. Thomas Parker (Brad Branch). Dr. Parker is out, but Meredith Parker (Debra Martuscello Wiley), his wife, takes an instant shine to the pathetic creature, convincing her husband and her daughter Shelley (Megan Quinn) that it's their Christian duty to care for him. Shelley has a terrible crush on Ricky, and at first is inclined to torment the creature that bit Ricky's sister. Gradually, though, she too comes to care for the boy. Dr. Parker's jealousy grows as Meredith, in a Professor Higgins type fashion, teaches the bat boy (whom they have now named Edgar) how to communicate and function in society. The town's unease gives Dr. Parker the leverage he needs to turn people against the bat boy, blaming him for the rancher's cattle plague, and Shelley and Edgar have to deal with not only their growing love, but Edgar's very survival.

The performance is, in a single word, stunning. In two words, extraordinarily stunning. From the first chord of "Hold Me, Batboy," the audience is rocking, and hooked.

The best moments of "Bat Boy" are shared by Wiley and Butler, as she is the first to offer him not only unconditional love, but also slavish devotion. These are among the best performances of each of their prolific theatrical careers. Their duet, "Home for You," is as touching as it is amusing. Both performers have spectacular comedic timing, as well as a flair for the dramatic pause, and can turn from one to the other in a flash. Wiley's voice hangs hauntingly after each song, and Butler's tremendously powerful chords range from thundering to softly prayerful. These two are spectacularly well matched.

Megan Quinn, as Meredith's daughter, is absolutely adorable. Her turn from taunting teen to young woman unfolds slowly, with her most powerful emotions first simply shining softly from her eyes. Brad Branch, as Dr. Parker, is clearly a man on the verge of madness. His obsession with winning his wife's love back clouds his judgment beyond control; his "Dance With Me, Darling," number lets us peek into the Mr. Hyde side of his character. Branch, too, lets subtlety guide him, and his insanity is that much more horrifying because of it. Bill Humphreys, as the sheriff who wants to do the right thing-if only someone would tell him what it is-makes use of his many comedic moments.

The ensemble is energetic and enthusiastic, and each actor capably handles the task of switching roles from character to character, even while remaining onstage-by putting on a hat, or removing a wig, or completely changing mannerisms and voices, sometimes going right back to the original character after a line or two. Choreographer Adrienne Maitland has created simple but sharp steps that support the action. The set, by Dane E. Leeman, allows for a number of vital acrobatics by the actors, yet is remarkably understated, as are the costumes by Chris Stolpe. Sarah Gurfield, director, has done a fabulous job at pulling this tale together. Your summer won't be complete without stopping in at this must-see show.

"Bat Boy" runs through Aug. 29 at Seacoast Repertory Theatre, 125 Bow St., Portsmouth, Thursdays at 7:30 p.m., Fridays at 8 p.m., Saturdays at 4 and 8 p.m. and Sundays at 3 p.m. Ticket prices range from $22 to $30. For reservations, call 603-433-4472.