In the days long ago before he'd hit the big four-oh, Dismas Hardy used to jog regularly. His course ran from his house on Thirty-fourth Avenue out to the beach, then south on the hard sand to Lincoln Way, where he'd turn east and pound the sidewalk until he got to Ninth and the bar he co-owned, the Little Shamrock. If it was a weekend or early evening, he'd often stop here to drink a beer before age wised him up and slowed him down. Later on, the beverage tended to be a glass of water. He'd finish his drink and conclude the four-mile circuit through Golden Gate Park and back up to his house.

The last time he'd gotten committed to an exercise program, maybe three years ago, he'd made it the first week and then about halfway through the second before he gave up, telling himself that two miles wasn't bad for a forty-seven-year-old. He'd put on a mere eight pounds this past decade, much less than many of his colleagues. He wasn't going to punish himself about his body, the shape he was in.

But then last year, his best friend, Abe Glitsky, had a heart attack that turned out to be a very near thing. Glitsky was the elder of the two men by a couple of years, but still, until it happened, Hardy had never considered either himself or Abe anywhere near old enough to have heart trouble. The two men had been best friends since they'd walked a beat together as cops just after Hardy's return from Vietnam.

Now Glitsky was the chief of San Francisco 's homicide detail. Half-black and half-Jewish, Glitsky was a former college tight end. No one among his colleagues would ever have thought of describing the lieutenant as anything but a hard-ass. His looks contributed to the rep as well-a thick scar coursed his lips top to bottom under a hatchet nose; he cultivated a fiercely unpleasant gaze. A buzz-cut fringe of gray bounded a wide, intelligent forehead. Glitsky didn't drink, smoke, or use profanity. He would only break out his smile to terrify staff (or small children for fun). Six months ago, when he'd married Treya Ghent, the administrative assistant to the new district attorney, several of his inspectors had bet that the new lifestyle would mellow him out considerably. They were still paying the installments.

Hardy was a successful defense attorney. Though he and Glitsky were on opposite sides of the fence professionally, there was also most of a lifetime of history between them. When Glitsky's first wife, Flo, had died some years before, Hardy and his wife, Frannie, had taken his three boys in to live with them until Abe could work his way through some of the emotional and logistical upheaval. Last fall, Hardy had been the best man at Abe's wedding.

They didn't talk about it-they were guys after all-but each was a fixed point of reference in the other's life.

The heart attack got their attention.

Since a month or so after Abe's marriage, they'd fallen into some semblance of a regular exercise program, where a couple of days a week one would goad or abuse the other into agreeing to do something physical. After the macho need to demonstrate their awesome strength and breathtaking endurance to each other in the first few weeks had almost made them quit the whole thing because of all the aches and pains, they finally had arrived at a brisk walk a couple of times a week, or perhaps throwing some kind of ball on the weekend.

This morning they were eating up maybe three miles an hour walking on the path around Stow Lake in Golden Gate Park. It was a cool and clear morning, the sun visible in the treetops. A mist hung over the water, and out of it at the near shore a swan with her brood of cygnets appeared.

Glitsky was talking work, as usual, complaining about the politics surrounding the appointment of two inexperienced inspectors to his detail of elite investigators in reaction to the unexplainable renaissance of hit-and-run accidents in the City by the Bay. In the past twelve months, Glitsky was saying, ninety-three persons had been struck by motor vehicles within the city and county. Of these, twenty-seven had died. Of the sixty-six injury accidents that didn't result in deaths, fourteen were hit and runs.

"I love it how you rattle off all those numbers," Hardy said. "Anybody would swear you knew what you were talking about."

"Those are the real stats."

"I'm sure they are. Which is why I'm glad we're on this path and not the street where we could be senselessly run down at any moment. But how do these numbers affect your department? I thought hit and runs weren't homicides."

Glitsky glanced sideways at him. "Technically, they are when somebody dies."

"Well, there you go. That's why they come to you. You're the homicide detail."

"But we don't investigate them. We have never investigated them. You want to know why? First, because there's a separate detail cleverly named 'hit and run.'"

"That's a good name if they do what I think," Hardy said.

"It's a fine name," Glitsky agreed. He knew, although the police department would deny it as a matter of course, that no hit-and-run incidents-even the homicides-were more than cursorily investigated by inspectors. What usually happened was that a couple of members of the hitand-run detail would take the paperwork at the Hall of Justice the day after the incident. Maybe they would go to the scene of an accident and see if they could find a witness to provide a description or license number of the vehicle. If that failed, and there were no good eyewitnesses in the report, that was essentially the end of the investigation. If they had a license number, they punched it into their computers to see if they had a street address associated with the vehicle. Sometimes, if the accident got a lot of press and they had a vehicle description, they would call a body shop or two and see if any cars matching the hit-and-run vehicle had surfaced. Usually the answer was no. "It's a fine department, even. But it doesn't do what we do, which is investigate murders."

"In spite of your detail's name, which indicates an interest in all homicides."

"Hence the confusion," Glitsky said. "Some of our civic leaders remain unclear on the concept."

They walked in silence for another moment. "What's second?" Hardy asked.

"What's second what?"

"You said you don't investigate hit-and-run homicides, first, because there's a separate hit-and-run detail. When you say first, it implies there's a second."

Glitsky's pace slackened; then both men stopped. "Second is that hit-and-run homicides tend not to be murders. In fact, they're never murders."

"Never say never."

"This time you can. You want to know why?"

"It's hard to ditch the murder weapon?"

"That's one reason. Another is that it's tough to convince your intended victim to stand in front of your car when there are no witnesses around so you can run him over. Most people just plain won't do it."

"So what's the problem?"

"The problem," Glitsky said, "is that with twenty-seven dead people in twelve months, the citizenry is apparently alarmed."

"I know I am," Hardy commented. "Perpetually."

"Yeah, well, as you may have read, our illustrious Board of Supes has authorized special funding for witness rewards and to beef up the investigation of all vehicular homicides."

"And a good idea it is."

"Wrong. It's a bad idea," Glitsky said. "There's no special investigation of vehicular homicides to begin with, not even in hit and run. Ninety percent of 'em, you got a drunk behind the wheel. The other ten percent, somebody's driving along minding their own business and somebody runs out from between two cars in front of them-blam! Then they freak and split. They probably weren't even doing anything wrong before they left the scene. These are felony homicides, okay, because the driver is supposed to stick around, but they are not murders."