ONE OF THE APPEALS of June Callwood as an author is that she writes books about Canadian people and subjects that other authors wouldn`t touch with a 10-foot pencil. She has written about an obscure, troubled woman who got a jail term for spying as a result of Igor Gouzenko`s revelations, She did a book about the friends of a woman who was dying of cancer and another about a man -- a gay Jehovahs Witness -- who survived longer than anyone with AIDS. Now, in The Sleepwalker, she writes about a young man who stabbed his mother-in-law to death while he was sleepwalking. It`s a terrific book. The young man in the case was Ken Parks, 23 years old, a big, bearish, amiable, decent guy without a whole lot of self esteem. He was married to a fine woman and had a baby daughter and got on like gangbusters with his in-laws. They provided him with the family that, coming from a background of parental strife, he never had. His major difficulty in life was that he tried far too hard to provide his wife and child with everything he thought they deserved: a house, security, a splashy holiday. He had a good job, but to step up the inflow of cash, he started to bet on the horses. He lost. He embezzled money from his employer, intending to repay as soon as his horse came in. It never did. When his embezzlement reached $30,000, he was caught. In the early hours of May 24, 1987, Ken Parks -- exhausted, out of work, broke, facing a trial, demoralized, at odds with the wife he loved -- got up from the living-room couch where he`d been sleeping, drove 14 miles from his home in Pickering, Ontario, to his in-laws` place in Scarborough, wounded his father-in-law, and killed his mother-in-law. To this day, he has no memory of these events. All he knew, immediately after the killing, was that he was covered in blood. He drove to a police station, frantic and bewildered, and was charged with first-degree murder. Weird? Things got even weirder, though much Clearer, at Ken Parks`s trial. It was his enormous good fortune that he stumbled into the hands of a brilliant criminal lawyer. Her name is Marlys Edwardh, and it was she who figured out the defence of sleepwalking. Parks`s family had a history of doing strange things without waking up -- walking, talking, getting dressed, cooking (though not eating) meals of steak, onions, and fries. Was it such a leap from those activities to murdering a mother-in-law? Not according to the psychiatrists and experts on sleep whom Edwardh marshalled for Parkss trial. This is what one psychiatrist testified at the trial: "There are a significant number of cases of aggression during sleepwalking and even of homicide." And: "Most sleepwalking episodes last between 10 and 40 minutes, but there are well-documented cases that last much longer." And more: "When awakened, the Sleepwalker has no recall and no explanation of what happened." And yet again: It is impossible, for instance, that a person could formulate a plan before falling asleep and then carry it out while sleepwalking. The most striking feature of what we know of what goes on in the mind during sleep is that it`s very independent of waking mentation. Marlys Edwardh argued to the jury trying Ken Parks that his actions in killing his mother-in-law were an instance of non-insane automatism. That is, Parks wasn`t crazy, and his behaviour was unconscious and involuntary. The jury bought the argument and acquitted Parks. The crown appealed the verdict, and as of August 1990, the Ontario Court of Appeal still hadn`t handed down a decision on the appeal. June Callwood, in her customary graceful and efficient prose, makes this story intimate and heartbreaking. She seems to have interviewed everyone connected to the case, and she seems to have addressed every question that rises to the reader`s lips. How does Parks`s wife feel about a husband who killed her mother? How have the families on both sides reacted to the tragedy? How about Parks? Has he been able to Put his life back in something like order and normalcy? All the questions arc answered. That includes perhaps the most scary question: is Parks likely to have another episode of homicidal sleepwalking? The answer is an unequivocal no.