Message to `Sendercorp': The blend is too bland Return to Sender Play by Bill Obrecht.

Entering the La Mama theater to see ``Return to Sender'' is like stepping into a spaceship. As the lights dim, you put on special gear for the expedition -- a trusty pair of 3-D glasses -- and watch the backdrop jump alive with projected images, designs, and mysterious messages from something called Sendercorp. Those messages, and the story behind them, become clear as the play proceeds. The four characters are on a space journey that keeps getting longer as technical glitches delay the landing date. To pass the time, they plug their minds into a ``blender'' -- a futuristic entertainment device that pumps stories directly into the brain, giving users the illusion of taking part in the action.

But the ``blender'' has a health warning attached: Overuse can diminish your ability to distinguish between ``blend'' reality and ``real'' reality. And that's not the only problem, as we learn later in the show. It seems the folks at Sendercorp, who make and market ``blenders,'' are a greedy lot with an itch not only for wealth, but for social control.

Although science-fiction fans have run into this sort of plot many times, it gives a chance for lots of story twists and visual surprises, and it has a worthwhile cautionary edge. This being so, it's too bad the creators of ``Return to Sender'' haven't done a more lively job. The action moves at a droopy pace, and the onstage performers (who lip-sync to a recorded tape of dialogue and music) don't generate much excitement. The idea of the show is clever. But its substance and stagecraft are below par.

``Return to Sender'' is the brainchild of musician Bill Obrecht, a colleague of such talents as Peter Gordon and Laurie Anderson, and of Perry Hoberman, whose 3-D slide show ``Out of the Picture (Return of the Invisible Man)'' was a memorable part of the recent biennial exhibition at the Whitney Museum of American Art here.