SIMON PETER SHEA, a protagonist saintly in name and nature, is the rock upon whom this novel is built. A retired professor who talks as though he were reading aloud, Simon is 76, and his old age is the "night" of the title.

The story turns on a question whose answer, for the reader with a heart as good as the author's, can never be in doubt: Should Simon retain his indepence? Or should he go into the Norman Home, where the other old folks are comically cracked, and where the proprietor, Hattie Norman, believes "God made TV to keep old people quiet"?

Because we see that the question is loaded, we hope that the answer will be surprising: something less simple than we (with our naive filial instincts, our Sunday-supplement altruism) expected. The answer, however, turns out to be exactly that simple. And so powerfully insisted upon that we are made to wonder whether there must not, after all, be something to be said for Hattie Norman.

Simon himself is passive. But in what amounts to a struggle for his soul, the "wicked" (Simon's adjective) Hattie Norman does have a virtuous adversary, the beautiful Dr. Jean Kirk. During their first conversation, this very young woman tells Simon what he should do with the rest of his life (return to his isolated cottage). Her self-assurance seems foolish and dangerous, but we wait in vain for someone wiser -- or for life itself -- to provide correction. Instead, Jean is placed in position to manipulate Simon's fate by means of an amazing coincidence, leading to everything she wants for him.

Much of the novel is devoted to flashback. We learn the stories of Simon's marriage and separation, and of his one brief love affair. This material from the past is richer, more lifelike, less subjugated to thematic significance, than is the main time frame of the story. It is the main story that perpetrates most of the sentimentality and also contains most of the padding: Simon's prayers quoted in their lengthy entirety; long, superbly articulate speeches in which total strangers pour out their grief to him.

The sense of place (small-town Minnesota) and time (election week, 1976) is strong. And there is wit:

"Shirley Lance's talk was full of initials. She referred to her daughter as Beebee and to her former husband as her Ex and to Simon as Mr. S. She said that when she was P.G. with Beebee, Doctor Kaye was her G.P. She said that her G.P. suspected that Beebee's I.Q. was sky-high, but that, of course, was on the Q.T. She said that her Ex, who was 1-A, would soon be off to war, and thus he had quit his job and was behind in his child support; last month, instead of money, he had sent her an I.O.U., the S.O.B."

If only the writing were often this lively, the observation this fresh. But instead it is largely page after page of this:

"'Here was a woman whose previous husband had been fatally wounded in a sudden, shocking accident, and we married so soon after his long and lingering death that her bereavement carried over into our marriage.'"

Polished prose? Yes. But this is supposed to be Simon speaking. What is wrong with it is, first, that nobody speaks that way; second, that if anyone did -- with those balanced rhythms, those carefully paired adjectives, that pattycake diction -- he would bore us to death. What is especially wrong with it is the quality of explanation, as in a lecture: The reader knows that he is its target. But what is most wrong of all is that we already have been shown this ghastly death, and shown what happened subsequent to it -- there shouldn't be, and there isn't, any need for a speech from the footlights afterward.

This is, to its credit, a socially conscious novel. But novels that champion causes need to cloak their advocacy in artifice. So it has proved for racial justice, gay pride, women's liberation. And so it is, as Simon's Night unfortunately demonstrates, for the liberation of old people.

"A novel is an impression," Thomas Hardy observed, "not an argument." A novelist with a cause does well to make it a concealed weapon; to tell an innocent-seeming story while preparing to stab us through his cape. He should breathe in our ears, cover our eyes, gently turn us soft-side-to. If not, his novel -- like Simon's Night -- won't pierce us; rather, it will lost its point.