PUZZLING. That about sums up the Loeb's production of The Children's Hour. Why, with a professional visiting director who presumably had her pick of Harvard actors, does the production leave the viewer so detached? Part of the answer undoubtedly rests with Lillian Hellman's somewhat dated play, and director Ella Gerber's unwillingness to delete certain overwritten scenes and lines. But the real and distirbing problem lies with the actors, who display about as much conviction and sinceretiy as marionettes.

Hellman's play depicts the plight of two schoolteachers, Martha Dobie (Jenny Cornuelle) and Karen Wright (Becky Stone), whose school for girls is threatened by the spitefulness of a spoiled, self-centered child who defies the women's sincere efforts to understand her resentment. When the child, Mary Tilford (Patrice Dabrowski), receives a just punishment for a series of rule infractions, she fabricates a tale that the schoolteachers are lesbians, convincing her grandmother (Cynthis Weinrich) to withdraw her and the other girls from the school. The teachers countersuit for slander fails, in part because Martha's aunt (Amy Aquino) refuses to testify in her defense. The mud sticks and destroys the lives of the teachers.

Although lesbianism itself fails to spark the emotional horror of the late '30s, Hellman's theme of irresponsible malice and perverted righteousness still rings true, even if the power of her tale is marred by several melodramatic scenes, slightly overdrawn characterizations, and an appalling denouement.

VISITING DIRECTOR Ella Gerber has stayed Hellman's more searing moments with expert clarity, and has given the production a professional rhythm. The actors, however mechanically they drone their lines, pick up on cues and set the swift pace essential for building and maintaining tension. Gerber displays a deft hand for creating effective stage pictures. When Mary extorts the gossip from her schoolmates that she will use to tar Karen and Martha, Gerber places her high above them on a ladder, smiling evilly down on the hapless girls. Again, during the scene of Mary's accusation, Gerber stands the teachers just outside the room, their faces shadowed by elaborate lattice doors.

However, if Gerber merits praise for her professional competence, she also deserves blame for failing to coax the actors into displaying any sincere emotions. The annoyingly overarticulated speech and tightly disciplined movements suggests relentless drilling, which has paid off in unremittingly mechanical deliveries. Nor do most of the actors bother to vary their volume or pitch effectively, even in critical scenes.

Becky Stone and Jenny Cornuelle as Karen and Martha turn in disappointingly wooden performances, livened by occasional flashes of emotion which suggest these actresses have untapped potential. Stone generally sleepwalks through her part, but she does convey authority and kindness when talking with the children, especially the terrorized Rosalie (Alice Brown--in the best performance of all the children).

Cornuelle suffers from a tendancy toward repetitious speech rhythms and oddly placed emphasis. Because she is so unconvicing in her original fight with her aunt and with Karen's fiance, her intensity in the climactic confession scene with Karen jolts one into surprised attention. Subtly shifting her volume at key moments, she effectively conveys Martha's inner struggle while dropping most of the distracting gestures and grimaces she has employed elsewhere.

Unfortunately, Patrice Dabrowski as the spoiled, malicious Mary Tilsford fares worse. Mary is a brooding manipulator, but Dabrowski plays her as a stereotyped bratty kid with stuck-out chin and petulant voice. While she sporadically succeeds at suggesting evil incarnate--especially in her scene with the frightened Rosalie--she never presents an appropriate psychological portrait, leaning always toward caricature.

Of the major characters, Amy Aquino as the theatrical, selfish Lily Mortar stands out, delivering a credible performance in one of the less skillfully written parts in the show. Although she starts out overly shrill and theatrical, Aquino emanates deliberate maliciousness in the pivotal scene with Martha, and her sharp jabbing at her embroidery all the while is a nice touch. Aquino even manages to avoid looking ridiculous in the last scene, where she must indulge in hysterics over Martha's death. Gerber would have done well to cut that last scene, for it drags on and on while recriminations fly.

IF THE ACTORS move about like puppets, at least they do so in Chris Kaseta's appropriate, well-designed set. The play opens on a warm, paneled schoolroom/livingroom, stuffed with comfortable chairs. Its large barnlike double doors and grainy wood evoke the farmland surrounding the girls' school. When the scene changes to the wealthy Mrs. Tilford's home, the ice blue and green furnishings set the tone of chilly splendor.

Nevertheless, the technical competence of this production cannot compensate for the actors' stiffness in a play whose success depends on skillful performances. Acting workshops and classes all over the country use scenes from Hellman's play to train budding thespians. For her play is a true actor's play, crying out for sophisticated character interpretation, development, and execution. It just isn't there.

Admittedly, parts of last Saturday's older crowd felt intermittently gripped. One woman, referring to the spoiled girl's lying accusations, was heard to say to her companion. "If I'd had that child alone for five minutes. I'd have gotten the truth out of her." At least somebody was into it.