WATSON'S APOLOGY. By Beryl Bainbridge. McGraw-Hill. 222 pp. $14.95.

THE IMPULSE which draws writers to recreate long-ago murders in their fiction is not difficult to understand: here is a bloody drama that has been played out, yet the curtain can always be rung up again and the actors put once more through their paces.

Not only, then, is the author omniscient in the usual manner but now holds sway over persons who actually witnessed, suffered or committed unspeakable acts. Says Beryl Bainbridge, in her brief prefatory note to Watson's Apology which explains that it is based on a true Victorian case, "What has defeated historical inquiry has been the motives of the characters, their conversations and their feelings. These it has been the task of the novelist to supply."

And so she does, in typical Bainbridge fashion -- the meticulous accumulation of unsettling small events, the persistent sounding of off-key notes, the imaginative instinct for the place where banality and derangement intersect. Thus, what might be remarkable for another writer, that the crime -- an elderly man kills his elderly wife -- which inspired the book is so very ordinary, is for her its consummate feature.

Watson's Apology opens with six peculiar letters of courtship, sent by an obviously unworldly and awkward schoolmaster to an impoverished old maid. Though they were never introduced, John Selby Watson has continued to cherish the memory of Miss Anne Armstrong since once catching a glimpse of her many years before. Deciding at last to marry, he can think only of the entrancing figure dressed in some bright shade of pink or lilac and "that . . . same husky intonation of voice which he had picked out above all others in that crowded drawing- room in Marlborough Street."

Not exactly an unlikely match -- each would otherwise remain single -- it is, nonetheless, according to Bainbridge's psychological portraiture, doomed from the very start. The foreshadowing is hardly subtle, but the reader, like the two inept lovers, is both mesmerized and disoriented at the same time. Perhaps, even, it is the disorientation itself which casts the spell.

At their second meeting, Watson watches the face of his bride-to-be who is, of course, something quite different from his memory of her, and it seems to him "that when she looked at him directly the melancholy little room with its dusty curtains and dark linoleum was swept by flame." For her part, Anne forces herself "to look sympathetically at Watson, but it (is) a terrible effort." Still, within four days, they join their lives together and for nearly 30 years more exist in a state of mutual torment.

Neither of them, for entirely different reasons, dwells altogether in the realm of reality. United by deep, thwarted yearnings to love and be loved, Watson and Anne struggle to communicate in a world where today's easily tossed-off jargon of self-realization, the language of Relationship, hasn't yet been invented. "She had overestimated his faculty for understanding; he had always underestimated her capacity for feeling."

When we hear this analysis, for example, it's hard to tell whether it is Bainbridge's authorial voice speaking, or Anne's own recognition. If it is the latter, though, what good does it do her? She, like her husband, is incapable of connecting self-awareness to action, and any efforts made by either in this direction seem like a sort of dementia.

This, added to the impossibility of the one seeing the other as he/she actually is creates a marital dance of death relentlessly choreographed by Bainbridge. Fascinated as ever by the hollow cavities where lie human pain, she steadily marks the ugly moments in which, for the luckless Watsons, frustrations and bitterness take the place of any simple companionability.

THE STORY of these two pathetic creatures is unfolded in Bainbridge's tantalizing style, which gives the reader the impression that something is happening just out of earshot, some detail which would make it all come right or at least render it less allusive and opaque. It's creepy, sad and suspenseful, all at once, the way she summons up the wraiths of "the strange murder at Stockwell," and the confusion between victim and villain is deliberate, given this 20th-century backward look.

Like all recreations of murders of centuries past, Watson's Apology has the slightly unpleasant smell of yellowing documents and mildewed carpets. The passions that gave rise to it were musty too, however, until Bainbridge decided to exhume them. Then, with her, one revisits both the quick and the dead -- now all deceased -- and regards the spectacle of witnesses whose own lives were made memorable only by proximity to such unnatural behavior.

Wickedly, too, Bainbridge, by choosing such a commonplace but once celebrated crime, reveals the inevitable forgetfulness of a public which lusted for details, then turned its attention quickly elsewhere. Inside the gory, outward sensation, she reminds us, were fully dimensional people -- by her reckoning, a querulous spinster manque,e and a pedantic hack who tried, haplessly, to love one another.