The National Theater of the Deaf's pro- duction of "Parzival: From the Horse's Mouth" demands to be loved. The show at the Terrace Theater, though, is only occasionally lovable.

Written by David Hays and Shanny Mow, it's a two-act takeoff on Arthurian legend, with knights, ladies, monsters and quests. The story of the young knight Parzival and his faithful horse Nevefere carries a lot of fine sentiments about deafness and deprivation. The good intentions, alas, don't make for good theater.

Most in the company use sign language, with two actors speaking the lines -- making the doings accessible to the deaf and the hearing alike. The cast is spirited and the staging imaginative -- for example, The Questing Beast, a fearsome monster played by three tangled actors, and Charles Baird's impression of a hawk attacking a rabbit.

But the script sometimes seems self- consciously cute, even as it embraces the aggressively educational. Forsaking dramatic integrity, the actors regularly step out of character to give personal witness to deafness -- which literally stops the show.

At one jarring point, the actor playing a hermit, Tetsuya Izaki, leaps off onto an autobiographical tangent about operating a kiln in art school, joining a Japanese deaf theater club and marching "to commemorate the 37th anniversary of Hiroshima and Nagasaki," thus "imprinting the gruesome negative of death on American eyes."

After that, it's magically back to King Arthur's court. PARZIVAL -- At the Terrace Theater through Saturday.